Debating 101 - Logic Fallacies


There's a lot of debate on the net.
Unfortunately, much of it is of very low quality.
The aim of this document is to explain the basics of logical fallacies (errors in logic),
and hopefully improve the overall quality of debate.
I will use Trek comments as samples.
These will GREATLY help you debate!

NOTE: I strongly recommend that you do NOT post a link to this page in a
public forum! The "other side" could see the link and use this info!!  Keep it a
secret among your fellow Kirk fans!

Enjoy!



What is a Fallacy?

In order to understand what a fallacy is, one must understand what an argument is. Very briefly, an argument consists of one or more premises and one conclusion. A premise is a statement (a sentence that is either true or false) that is offered in support of the claim being made, which is the conclusion (which is also a sentence that is either true or false).

There are two main types of arguments: deductive and inductive. A deductive argument is an argument such that the premises provide (or appear to provide) complete support for the conclusion. An inductive argument is an argument such that the premises provide (or appear to provide) some degree of support (but less than complete support) for the conclusion. If the premises actually provide the required degree of support for the conclusion, then the argument is a good one. A good deductive argument is known as a valid argument and is such that if all its premises are true, then its conclusion must be true. If all the argument is valid and actually has all true premises, then it is known as a sound argument. If it is invalid or has one or more false premises, it will be unsound. A good inductive argument is known as a strong (or "cogent") inductive argument. It is such that if the premises are true, the conclusion is likely to be true.

A fallacy is, very generally, an error in reasoning. This differs from a factual error, which is simply being wrong about the facts. To be more specific, a fallacy is an "argument" in which the premises given for the conclusion do not provide the needed degree of support. A deductive fallacy is a deductive argument that is invalid (it is such that it could have all true premises and still have a false conclusion). An inductive fallacy is less formal than a deductive fallacy. They are simply "arguments" which appear to be inductive arguments, but the premises do not provided enough support for the conclusion. In such cases, even if the premises were true, the conclusion would not be more likely to be true.

Examples of Fallacies

1. Inductive Argument

Premise 1: Most American cats are domestic house cats.
Premise 2: Bill is an American cat.
Conclusion: Bill is domestic house cat.

2. Factual Error

Columbus is the capital of the United States.

3. Deductive Fallacy

Premise 1: If Portland is the capital of Maine, then it is in Maine.
Premise 2: Portland is in Maine.
Conclusion: Portland is the capital of Maine.
(Portland is in Maine, but Augusta is the capital. Portland is the largest city in Maine, though.)

4. Inductive Fallacy

Premise 1: Having just arrived in Ohio, I saw a white squirrel.
Conclusion: All Ohio Squirrels are white.
(While there are many, many squirrels in Ohio, the white ones are very rare).


Fallacies Of Distraction

Each of these fallacies is characterized by the illegitimate use of a logical operator
in order to distract the reader from the apparent falsity of a certain proposition.

The following fallacies are fallacies of distraction:

1. False Dilemma / Bifurcation

DEFINITION: A limited number of options (usually two) is given, while in reality there are more options. A false dilemma is an illegitimate use of the "or" operator.

Putting issues or opinions into "black or white" terms is a common instance of this fallacy.

EXAMPLE: "America: love it or leave it."

PROOF: Identify the options given and show (with an example) that there is an additional option. (Kirk may have kissed a girl or two, but not ALL of them or NONE of them.)

2. Argument from Silence / Argument from Ignorance (argumentum ad ignorantiam)

DEFINITION: Arguments of this form assume that since something has not been proven false, it is therefore true. Conversely, such an argument may assume that since something has not been proven true, it is therefore false. (This is a special case of a false dilemma, since it assumes that all propositions must either be known to be true or known to be false.) As Davis writes, "Lack of proof is not proof."

EXAMPLE: "You cannot prove that ghosts do not exist.  Therefore they do ."

PROOF:  Identify the proposition in question. Argue that it may be true even though we don't know whether it is or isn't.

3. Shifting the Burden of Proof

DEFINITION: The burden of proof is always on the person asserting something. Shifting the burden of proof, a special case of Argumentum ad Ignorantiam, is the fallacy of putting the burden of proof on the person who denies or questions the assertion. The source of the fallacy is the assumption that something is true unless proven otherwise.

Burden of Proof is a fallacy in which the burden of proof is placed on the wrong side. Another version occurs when a lack of evidence for side A is taken to be evidence for side B in cases in which the burden of proof actually rests on side B. This sort of reasoning typically has the following form:

1. Claim X is presented by side A and the burden of proof actually rests on side B.
2. Side B claims that X is false because there is no proof for X.

In many situations, one side has the burden of proof resting on it. This side is obligated to provide evidence for its position. The claim of the other side, the one that does not bear the burden of proof, is assumed to be true unless proven otherwise. The difficulty in such cases is determining which side, if any, the burden of proof rests on. In many cases, settling this issue can be a matter of significant debate. In some cases the burden of proof is set by the situation. For example, in American law a person is assumed to be innocent until proven guilty (hence the burden of proof is on the prosecution). As another example, in debate the burden of proof is placed on the affirmative team. As a final example, in most cases the burden of proof rests on those who claim something exists (such as Bigfoot, psychic powers, universals, and sense data).

EXAMPLE: "I say that Bigfoot exists.  Now prove me wrong." (You don't have to prove them wrong.  THEY made the assertion, therefore THEY have to prove Bigfoot exists.)

4. Slippery Slope/ The Camel's Nose

DEFINITION: In order to show that a proposition P is unacceptable, a sequence of increasingly unacceptable events is shown to follow from P. A slippery slope is an illegitimate use of the "if-then" operator.

The Slippery Slope is a fallacy in which a person asserts that some event must inevitably follow from another without any argument for the inevitability of the event in question. In most cases, there are a series of steps or gradations between one event and the one in question and no reason is given as to why the intervening steps or gradations will simply be bypassed. This "argument" has the following form:

1. Event X has occurred (or will or might occur).
2. Therefore event Y will inevitably happen.

This sort of "reasoning" is fallacious because there is no reason to believe that one event must inevitably follow from another without an argument for such a claim. This is especially clear in cases in which there is a significant number of steps or gradations between one event and another.

EXAMPLE: "We have to stop the tuition increase! The next thing you know, they'll be charging $40,000 a semester!"

PROOF: Identify the proposition P being refuted and identify the final event in the series of events. Then show that this final event need not occur as a consequence of P.  

5. Complex Question / Fallacy of interrogation / Fallacy of presupposition

DEFINITION: Two otherwise unrelated points are conjoined and treated as a single proposition. The reader is expected to accept or reject both together, when in reality one is acceptable while the other is not. A complex question is an illegitimate use of the "and" operator.

EXAMPLE: "Have you stopped beating your wife?" (This asks two questions: Did you beat your wife, and did you stop?)

PROOF: Identify the two propositions illegitimately conjoined and/or show that believing one does not mean that you have to believe the other.


Appeals to Motives in Place of Support

The fallacies in this section have in common the practise of appealing to emotions or other psychological factors.
In this way, they do not provide reasons for belief.

The following fallacies are appeals to motive in place of support:

1. Appeal To Force (Argumentum ad baculum ) / Appeal To Fear / Scare Tactics

DEFINITION: The reader is told that unpleasant consequences will follow if they do not agree with the author.

This fallacy has the following pattern:

1. Y is presented (a claim that is intended to produce fear).
2. Therefore claim X is true (a claim that is generally, but need not be, related to Y in some manner).

This line of "reasoning" is fallacious because creating fear in people does not constitute evidence for a claim.

It is important to distinguish between a rational reason to believe evidence that objectively and logically supports the claim, and a prudential reason to accept the belief because of some external factor (such as fear, a threat, or a benefit or harm that may stem from the belief) that is relevant to what a person values but is not relevant to the truth or falsity of the claim. For example, it might be prudent to not fail the son of your department chairperson because you fear he will make life tough for you. However, this does not provide evidence for the claim that the son deserves to pass the class.

EXAMPLE: "You had better agree that the new company policy is the best if you expect to keep your job."

PROOF: Identify the threat and the proposition and argue that the threat is unrelated to the truth or falsity of the proposition.

2. Appeal to Pity (argumentum ad misercordiam)

DEFINITION: The reader is told to agree to the proposition because of the pitiful state of the author.

An Appeal to Pity is a fallacy in which a person substitutes a claim intended to create pity for evidence in an argument. The form of the "argument" is as follows:

1. P is presented, with the intent to create pity.
2. Therefore claim C is true.

This line of "reasoning" is fallacious because pity does not serve as evidence for a claim. This is extremely clear in the following case: "You must accept that 1+1=46, after all I'm dying..." While you may pity me because I am dying, it would hardly make my claim true.

This fallacy differs from the Appeal to the Consequences of a Belief. In that fallacy, a person is using the effects of a belief as a substitute for evidence. In the Appeal to Pity, it is the feelings of pity or sympathy that are substituted for evidence.

It must be noted that there are cases in which claims that actually serve as evidence also evoke a feeling of pity. In such cases, the feeling of pity is still not evidence. The following is an example of a case in which a claim evokes pity and also serves as legitimate evidence:

Professor: "You missed the midterm, Bill."
Bill: "I know. I think you should let me take the makeup."
Professor: "Why?"
Bill: "I was hit by a truck on the way to the midterm. Since I had to go to the emergency room with a broken leg, I think I am entitled to a makeup."
Professor: "I'm sorry about the leg, Bill. Of course you can make it up."

The above example does not involve a fallacy. While the professor does feel sorry for Bill, she is justified in accepting Bill's claim that he deserves a makeup. After all getting run over by a truck would be a legitimate excuse for missing a test.

EXAMPLE: "Stop arguing with me about how leprechans are fake.  They are real, and I am tired and was sick yesterday, so just let this debate go."

PROOF: Identify the proposition and the appeal to pity and argue that the pitiful state of the arguer has nothing to do with the truth of the proposition.

3. Appeal to Consequences (argumentum ad consequentiam)

DEFINITION: The author points to the disagreeable consequences of holding a particular belief in order to show that this belief is false.

EXAMPLE: "You can't agree that evolution is true, because if it were, then we would be no better than monkeys and apes."

PROOF: Identify the consequences to and argue that what we want to be the case does not affect what is in fact the case.

4. Prejudicial Language

DEFINITION: Loaded or emotive terms are used to attach value or moral goodness to believing the proposition.

EXAMPLE (italics indicate the prejudicial language): "A reasonable person would agree that our income statement is too low."

PROOF: Identify the prejudicial terms used. Such as in the example, show that disagreeing with the conclusion does not make a person "unreasonable".

5. Appeal to Popularity (argumentum ad populum)

DEFINITION: These are also known as Appealing to the Gallery, or Appealing to the People. You commit this fallacy if you attempt to win acceptance of an assertion by appealing to a large group of people. This form of fallacy is often characterized by emotive language.

The Appeal to Popularity has the following form:

1. Most people approve of X (have favorable emotions towards X).
2. Therefore X is true.

The basic idea is that a claim is accepted as being true simply because most people are favorably inclined towards the claim. More formally, the fact that most people have favorable emotions associated with the claim is substituted in place of actual evidence for the claim. A person falls prey to this fallacy if he accepts a claim as being true simply because most other people approve of the claim.

It is clearly fallacious to accept the approval of the majority as evidence for a claim. For example, suppose that a skilled speaker managed to get most people to absolutely love the claim that 1+1=3. It would still not be rational to accept this claim simply because most people approved of it. After all, mere approval is no substitute for a mathematical proof. At one time people approved of claims such as "the world is flat", "humans cannot survive at speeds greater than 25 miles per hour", "the sun revolves around the earth" but all these claims turned out to be false.

This sort of "reasoning" is quite common and can be quite an effective persusasive device. Since most humans tend to conform with the views of the majority, convincing a person that the majority approves of a claim is often an effective way to get him to accept it. Advertisers often use this tactic when they attempt to sell products by claiming that everyone uses and loves their products. In such cases they hope that people will accept the (purported) approval of others as a good reason to buy the product.

This fallacy is vaguely similar to such fallacies as Appeal to Belief and Appeal to Common Practice. However, in the case of an Ad Populum the appeal is to the fact that most people approve of a claim. In the case of an Appeal to Belief, the appeal is to the fact that most people believe a claim. In the case of an Appeal to Common Practice, the appeal is to the fact that many people take the action in question.

This fallacy is closely related to the Appeal to Emotion fallacy, as discussed in the entry for that fallacy.

6. Appeal to Emotion

DEFINITION: An Appeal to Emotion is a fallacy with the following structure:

1. Favorable emotions are associated with X.
2. Therefore, X is true.

This fallacy is committed when someone manipulates peoples' emotions in order to get them to accept a claim as being true. More formally, this sort of "reasoning" involves the substitution of various means of producing strong emotions in place of evidence for a claim. If the favorable emotions associated with X influence the person to accept X as true because they "feel good about X," then he has fallen prey to the fallacy.

This sort of "reasoning" is very common in politics and it serves as the basis for a large portion of modern advertising. Most political speeches are aimed at generating feelings in people so that these feelings will get them to vote or act a certain way. in the case of advertising, the commercials are aimed at evoking emotions that will influence people to buy certain products. In most cases, such speeches and commercials are notoriously free of real evidence.

This sort of "reasoning" is quite evidently fallacious. It is fallacious because using various tactics to incite emotions in people does not serve as evidence for a claim. For example, if a person were able to inspire in a person an incredible hatred of the claim that 1+1 = 2 and then inspired the person to love the claim that 1+1 = 3, it would hardly follow that the claim that 1+1 = 3 would be adequately supported.

It should be noted that in many cases it is not particularly obvious that the person committing the fallacy is attempting to support a claim. In many cases, the user of the fallacy will appear to be attempting to move people to take an action, such as buying a product or fighting in a war. However, it is possible to determine what sort of claim the person is actually attempting to support. In such cases one needs to ask "what sort of claim is this person attempting to get people to accept and act on?" Determining this claim (or claims) might take some work. However, in many cases it will be quite evident. For example, if a political leader is attempting to convince her followers to participate in certain acts of violence by the use of a hate speech, then her claim would be "you should participate in these acts of violence." In this case, the "evidence" would be the hatred evoked in the followers. This hatred would serve to make them favorable inclined towards the claim that they should engage in the acts of violence. As another example, a beer commercial might show happy, scantily clad men and women prancing about a beach, guzzling beer. In this case the claim would be "you should buy this beer." The "evidence" would be the excitement evoked by seeing the beautiful people guzzling the beer.

This fallacy is actually an extremely effective persuasive device. As many people have argued, peoples' emotions often carry much more force than their reason. Logical argumentation is often difficult and time consuming and it rarely has the power to spurn people to action. It is the power of this fallacy that explains its great popularity and wide usage. However, it is still a fallacy.

In all fairness it must be noted that the use of tactics to inspire emotions is an important skill. Without an appeal to peoples' emotions, it is often difficult to get them to take action or to perform at their best. For example, no good coach presents her team with syllogisms before the big game. Instead she inspires them with emotional terms and attempts to "fire" them up. There is nothing inherently wrong with this. However, it is not any acceptable form of argumentation. As long as one is able to clearly distinguish between what inspires emotions and what justifies a claim, one is unlikely to fall prey to this fallacy.

As a final point, in many cases it will be difficult to distinguish an Appeal to Emotion from some other fallacies and in many cases multiple fallacies may be committed. For example, many Ad Hominems will be very similar to Appeals to Emotion and, in some cases, both fallacies will be committed. As an example, a leader might attempt to invoke hatred of a person to inspire his followers to accept that they should reject her claims. The same attack could function as an Appeal to Emotion and a Personal Attack. In the first case, the attack would be aimed at making the followers feel very favorable about rejecting her claims. In the second case, the attack would be aimed at making the followers reject the person's claims because of some perceived (or imagined) defect in her character.

This fallacy is related to the Appeal to Popularity fallacy. Despite the differences between these two fallacies, they are both united by the fact that they involve appeals to emotions. In both cases the fallacies aim at getting people to accept claims based on how they or others feel about the claims and not based on evidence for the claims.

7. Appeal to Belief

DEFINITION: Appeal to Belief is a fallacy that has this general pattern:

1. Most people believe that a claim, X, is true.
2. Therefore X is true.

This line of "reasoning" is fallacious because the fact that many people believe a claim does not, in general, serve as evidence that the claim is true.

There are, however, some cases when the fact that many people accept a claim as true is an indication that it is true. For example, while you are visiting Maine, you are told by several people that they believe that people older than 16 need to buy a fishing license in order to fish. Barring reasons to doubt these people, their statements give you reason to believe that anyone over 16 will need to buy a fishing license.

There are also cases in which what people believe actually determines the truth of a claim. For example, the truth of claims about manners and proper behavior might simply depend on what people believe to be good manners and proper behavior. Another example is the case of community standards, which are often taken to be the standards that most people accept. In some cases, what violates certain community standards is taken to be obscene. In such cases, for the claim "x is obscene" to be true is for most people in that community to believe that x is obscene. In such cases it is still prudent to question the justification of the individual beliefs.

EXAMPLE: "Saddam was behind 9/11! The majority of Americans believe it!  Who are we do disagree with all these people?  Are you calling them stupid?"

PROOF: Identify the proposition and point out that just because many people feel a certain way, does not make those feelings a fact.

8. Appeal To Numbers (Argumentum ad numerum)

DEFINITION: This fallacy is closely related to the argumentum ad populum. It consists of asserting that the more people who support or believe a proposition, the more likely it is that that proposition is correct.

EXAMPLE:"The majority feel John's proposal is right. Therefore it's a fact."

PROOF: Identify the proposition and point out that just because many people believe a proposition to be true, does not mean the proposition IS true.


Changing the Subject

The fallacies in this section change the subject by discussing the person making
the argument instead of discussing reasons to believe or disbelieve the conclusion.
While on some occasions it is useful to cite authorities, it is almost never
appropriate to discuss the person instead of the argument.

1. Ad Hominem - Attacking the Person (argumentum ad hominem)

DEFINITION: The person presenting an argument is attacked instead of the argument itself. This takes many forms. For example, the person's character, nationality or religion may be attacked. Alternatively, it may be pointed out that a person stands to gain from a favourable outcome. Or, finally, a person may be attacked by association, or by the company he keeps.

Translated from Latin to English, "Ad Hominem" means "against the man" or "against the person."

An Ad Hominem is a general category of fallacies in which a claim or argument is rejected on the basis of some irrelevant fact about the author of or the person presenting the claim or argument. Typically, this fallacy involves two steps. First, an attack against the character of person making the claim, her circumstances, or her actions is made (or the character, circumstances, or actions of the person reporting the claim). Second, this attack is taken to be evidence against the claim or argument the person in question is making (or presenting). This type of "argument" has the following form:

1. Person A makes claim X.
2. Person B makes an attack on person A.
3. Therefore A's claim is false.

The reason why an Ad Hominem (of any kind) is a fallacy is that the character, circumstances, or actions of a person do not (in most cases) have a bearing on the truth or falsity of the claim being made (or the quality of the argument being made).

There are three major forms of Attacking the Person:

a. Ad Hominem (abusive): Instead of attacking an assertion, the argument attacks the person who made the assertion.

EXAMPLE: "You think tomatoes are fruits? That's because you are just stupid."

PROOF: Identify the attack and show that it has nothing to do with the truth or falsity of the proposition being defended.

b. Ad Hominem (circumstantial):

DEFINITION: Instead of attacking an assertion the author points to the relationship between the person making the assertion and the person's circumstances.

A Circumstantial ad Hominem is a fallacy in which one attempts to attack a claim by asserting that the person making the claim is making it simply out of self interest. In some cases, this fallacy involves substituting an attack on a person's circumstances (such as the person's religion, political affiliation, ethnic background, etc.). The fallacy has the following forms:

1. Person A makes claim X.
2. Person B asserts that A makes claim X because it is in A's interest to claim X.
3.Therefore claim X is false.

1. Person A makes claim X.
2. Person B makes an attack on A's circumstances.
3.Therefore X is false.

A Circumstantial ad Hominem is a fallacy because a person's interests and circumstances have no bearing on the truth or falsity of the claim being made. While a person's interests will provide them with motives to support certain claims, the claims stand or fall on their own. It is also the case that a person's circumstances (religion, political affiliation, etc.) do not affect the truth or falsity of the claim. This is made quite clear by the following example: "Bill claims that 1+1=2. But he is a Republican, so his claim is false."

There are times when it is prudent to suspicious of a person's claims, such as when it is evident that the claims are being biased by the person's interests. For example, if a tobacco company representative claims that tobacco does not cause cancer, it would be prudent to not simply accept the claim. This is because the person has a motivation to make the claim, whether it is true or not. However, the mere fact that the person has a motivation to make the claim does not make it false. For example, suppose a parent tells her son that sticking a fork in a light socket would be dangerous. Simply because she has a motivation to say this obviously does not make her claim false.

EXAMPLE: "Of course you don't like the Queen Mum.  You are not British like she is."

PROOF: Identify the attack and show that the circumstances has nothing to do with the truth or falsity of the proposition being defended.

c. Ad Hominem (tu quoque):

DEFINITION: This form of attack on the person notes that a person does not practise what he preaches. This fallacy is committed when it is concluded that a person's claim is false because 1) it is inconsistent with something else a person has said or 2) what a person says is inconsistent with her actions. This type of "argument" has the following form:

1. Person A makes claim X.
2. Person B asserts that A's actions or past claims are inconsistent with the truth of claim X.
3. Therefore X is false.

The fact that a person makes inconsistent claims does not make any particular claim he makes false (although of any pair of inconsistent claims only one can be true - but both can be false). Also, the fact that a person's claims are not consistent with his actions might indicate that the person is a hypocrite, but this does not prove his claims are false.

EXAMPLE: "You are making a stance that I shouldn't attack Democrats.  But you say bad things about Republicans all the time!"

PROOF: Identify the attack and show that it has nothing to do with the truth or falsity of the proposition being defended.

d. Genetic Fallacy

DEFINITION: Genetic Fallacy is a variation on Ad Hominem Circumstantial this in that instead of attacking an assertion the author points to the relationship between the person making the assertion and the person's genetic circumstances.

EXAMPLE: "He doesn't like Sarah because he is a man, and Sarah is a woman."

PROOF: Identify the attack and show that the genetic circumstances has nothing to do with the truth or falsity of the proposition being defended.

e. Poisoning The Well

DEFINITION:  Another variant of Ad Hominem Circumstantial.  This sort of "reasoning" involves trying to discredit what a person might later claim by presenting unfavorable information (be it true or false) about the person. This "argument" has the following form:

Unfavorable information (be it true or false) about person A is presented.
Therefore any claims person A makes will be false.

This sort of "reasoning" is obviously fallacious. The person making such an attack is hoping that the unfavorable information will bias listeners against the person in question and hence that they will reject any claims he might make. However, merely presenting unfavorable information about a person (even if it is true) hardly counts as evidence against the claims he/she might make. This is especially clear when Poisoning the Well is looked at as a form of Ad Hominem in which the attack is made prior to the person even making the claim or claims. The following example clearly shows that this sort of "reasoning" is quite poor.

EXAMPLE: "Don't listen to what he has to say, he is not a Baptist."

PROOF:  If the unfavorable information is untrue, you can choose to state the truth.  But regardless if the information is true or not: identify the attack and show that it has nothing to do with the truth or falsity of the proposition being defended.

2. Appeal to Authority (argumentum ad verecundiam)

DEFINITION: While sometimes it may be appropriate to cite an authority to support a point, often it is not.

An Appeal to Authority is a fallacy with the following form:

1. Person A is (claimed to be) an authority on subject S.
2. Person A makes claim C about subject S.
3. Therefore, C is true.

This fallacy is committed when the person in question is not a legitimate authority on the subject. More formally, if person A is not qualified to make reliable claims in subject S, then the argument will be fallacious.

This sort of reasoning is fallacious when the person in question is not an expert. In such cases the reasoning is flawed because the fact that an unqualified person makes a claim does not provide any justification for the claim. The claim could be true, but the fact that an unqualified person made the claim does not provide any rational reason to accept the claim as true.

When a person falls prey to this fallacy, they are accepting a claim as true without there being adequate evidence to do so. More specifically, the person is accepting the claim because they erroneously believe that the person making the claim is a legitimate expert and hence that the claim is reasonable to accept. Since people have a tendency to believe authorities (and there are, in fact, good reasons to accept some claims made by authorities) this fallacy is a fairly common one.

Since this sort of reasoning is fallacious only when the person is not a legitimate authority in a particular context, it is necessary to provide some acceptable standards of assessment. The following standards are widely accepted:

In particular, an appeal to authority is inappropriate if:

a. The person is not qualified to have an expert opinion on the subject.

Claims made by a person who lacks the needed degree of expertise to make a reliable claim will, obviously, not be well supported. In contrast, claims made by a person with the needed degree of expertise will be supported by the person's reliability in the area.

Determining whether or not a person has the needed degree of expertise can often be very difficult. In academic fields (such as philosophy, engineering, history, etc.), the person's formal education, academic performance, publications, membership in professional societies, papers presented, awards won and so forth can all be reliable indicators of expertise. Outside of academic fields, other standards will apply. For example, having sufficient expertise to make a reliable claim about how to tie a shoe lace only requires the ability to tie the shoe lace and impart that information to others. It should be noted that being an expert does not always require having a university degree. Many people have high degrees of expertise in sophisticated subjects without having ever attended a university. Further, it should not be simply assumed that a person with a degree is an expert.

Of course, what is required to be an expert is often a matter of great debate. For example, some people have (and do) claim expertise in certain (even all) areas because of a divine inspiration or a special gift. The followers of such people accept such credentials as establishing the person's expertise while others often see these self-proclaimed experts as deluded or even as charlatans. In other situations, people debate over what sort of education and experience is needed to be an expert. Thus, what one person may take to be a fallacious appeal another person might take to be a well supported line of reasoning. Fortunately, many cases do not involve such debate.

If a person makes a claim about some subject outside of his area(s) of expertise, then the person is not an expert in that context. Hence, the claim in question is not backed by the required degree of expertise and is not reliable.

It is very important to remember that because of the vast scope of human knowledge and skill it is simply not possible for one person to be an expert on everything. Hence, experts will only be true experts in respect to certain subject areas. In most other areas they will have little or no expertise. Thus, it is important to determine what subject area a claim falls under.

It is also very important to note that expertise in one area does not automatically confer expertise in another. For example, being an expert physicist does not automatically make a person an expert on morality or politics. Unfortunately, this is often overlooked or intentionally ignored. In fact, a great deal of advertising rests on a violation of this condition. As anyone who watches television knows, it is extremely common to get famous actors and sports heroes to endorse products that they are not qualified to assess. For example, a person may be a great actor, but that does not automatically make him an expert on cars or shaving or underwear or diets or politics.

EXAMPLE: "My husband works for the Salvation Army, and he says suicide is a good thing."

PROOF: Show that the source is not an authority on the subject.

b. Experts in the field disagree on this issue.

If there is a significant amount of legitimate dispute among the experts within a subject, then it will fallacious to make an Appeal to Authority using the disputing experts. This is because for almost any claim being made and "supported" by one expert there will be a counterclaim that is made and "supported" by another expert. In such cases an Appeal to Authority would tend to be futile. In such cases, the dispute has to be settled by consideration of the actual issues under dispute. Since either side in such a dispute can invoke experts, the dispute cannot be rationally settled by Appeals to Authority.

There are many fields in which there is a significant amount of legitimate dispute. Economics is a good example of such a disputed field. Anyone who is familiar with economics knows that there are many plausible theories that are incompatible with one another. Because of this, one expert economist could sincerely claim that the deficit is the key factor while another equally qualified individual could assert the exact opposite. Another area where dispute is very common (and well known) is in the area of psychology and psychiatry. As has been demonstrated in various trials, it is possible to find one expert that will assert that an individual is insane and not competent to stand trial and to find another equally qualified expert who will testify, under oath, that the same individual is both sane and competent to stand trial. Obviously, one cannot rely on an Appeal to Authority in such a situation without making a fallacious argument. Such an argument would be fallacious since the evidence would not warrant accepting the conclusion.

It is important to keep in mind that no field has complete agreement, so some degree of dispute is acceptable. How much is acceptable is, of course, a matter of serious debate. It is also important to keep in mind that even a field with a great deal of internal dispute might contain areas of significant agreement. In such cases, an Appeal to Authority could be legitimate.

EXAMPLE: "Roger Ebert is an established film critic, and he says The Phantom Menace is a good movie." (Though he is an expert on film, not all film critics agree that The Phantom Menace is a good movie.)

PROOF: Show that just because one expert makes an assertion, that there is general disagreement among the experts in the field on this point.

c. The authority was making a joke, drunk, or otherwise not being serious.

EXAMPLE: "Billy was accused of murder and he said to police. 'Oh, yeah, right. I did it. Sure.' This is proof that he did it."

PROOF: Show that the authority was not being serious.

d. The authority is biased

If an expert is significantly biased then the claims he makes within his are of bias will be less reliable. Since a biased expert will not be reliable, an Argument from Authority based on a biased expert will be fallacious. This is because the evidence will not justify accepting the claim.

Experts, being people, are vulnerable to biases and predjudices. If there is evidence that a person is biased in some manner that would affect the reliability of her claims, then an Argument from Authority based on that person is likely to be fallacious. Even if the claim is actually true, the fact that the expert is biased weakens the argument. This is because there would be reason to believe that the expert might not be making the claim because he has carefully considered it using his expertise. Rather, there would be reason to believe that the claim is being made because of the expert's bias or prejudice.

It is important to remember that no person is completely objective. At the very least, a person will be favorable towards her own views (otherwise she would probably not hold them). Because of this, some degree of bias must be accepted, provided that the bias is not significant. What counts as a significant degree of bias is open to dispute and can vary a great deal from case to case. For example, many people would probably suspect that doctors who were paid by tobacco companies to research the effects of smoking would be biased while other people might believe (or claim) that they would be able to remain objective.

e. The authority's expertise is not a legitmate area or discipline

Certain areas in which a person may claim expertise may have no legitimacy or validity as areas of knowledge or study. Obviously, claims made in such areas will not be very reliable.

What counts as a legitimate area of expertise is sometimes difficult to determine. However, there are cases which are fairly clear cut. For example, if a person claimed to be an expert at something he called "chromabullet therapy" and asserted that firing painted rifle bullets at a person would cure cancer it would not be very reasonable to accept his claim based on his "expertise." After all, his expertise is in an area which is devoid of legitimate content. The general idea is that to be a legitimate expert a person must have mastery over a real field or area of knowledge.

As noted above, determining the legitimacy of a field can often be difficult. In European history, various scientists had to struggle with the Church and established traditions to establish the validity of their discliplines. For example, experts on evolution faced an uphill battle in getting the legitimacy of their area accepted.

A modern example involves psychic phenomenon. Some people claim that they are certified "master psychics" and that they are actually experts in the field. Other people contend that their claims of being certified "master psychics" are simply absurd since there is no real content to such an area of expertise. If these people are right, then anyone who accepts the claims of these "master psychics" as true are victims of a fallacious appeal to authority.

f. Appeal to an Unnamed Authority / Anonymous Authorities

DEFINITION: The authority in question is not named. This is a type of appeal to authority because when an authority is not named it is impossible to confirm that the authority is an expert. However the fallacy is so common it deserves special mention. A common variation of the typical Appeal to Authority fallacy is an Appeal to an Unnamed Authority. This fallacy is also known as an Appeal to an Unidentified Authority.

This fallacy is committed when a person asserts that a claim is true because an expert or authority makes the claim and the person does not actually identify the expert. Since the expert is not named or identified, there is no way to tell if the person is actually an expert. Unless the person is identified and has his expertise established, there is no reason to accept the claim.

This sort of reasoning is not unusual. Typically, the person making the argument will say things like "I have a book that says...", or "they say...", or "the experts say...", or "scientists believe that...", or "I read in the paper.." or "I saw on TV..." or some similar statement. in such cases the person is often hoping that the listener(s) will simply accept the unidentified source as a legitimate authority and believe the claim being made. If a person accepts the claim simply because they accept the unidentified source as an expert (without good reason to do so), he has fallen prey to this fallacy.

EXAMPLE: "Experts agree that the Bible is 100% error-free."

PROOF: Argue that because we don't know the source of the information, we have no way to evaluate the reliability of the information.

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As suggested above, not all Appeals to Authority are fallacious. This is fortunate since people have to rely on experts. This is because no one person can be an expert on everything and people do not have the time or ability to investigate every single claim themselves.

In many cases, Arguments from Authority will be good arguments. For example, when a person goes to a skilled doctor and the doctor tells him that he has a cold, then the the patient has good reason to accept the doctor's conclusion. As another example, if a person's computer is acting odd and his friend, who is a computer expert, tells him it is probably his hard drive then he has good reason to believe her.

What distinguishes a fallacious Appeal to Authority from a good Appeal to Authority is that the argument meets the six conditions discussed above.

In a good Appeal to Authority, there is reason to believe the claim because the expert says the claim is true. This is because a person who is a legitimate expert is more likely to be right than wrong when making considered claims within her area of expertise. In a sense, the claim is being accepted because it is reasonable to believe that the expert has tested the claim and found it to be reliable. So, if the expert has found it to be reliable, then it is reasonable to accept it as being true. Thus, the listener is accepting a claim based on the testimony of the expert.

It should be noted that even a good Appeal to Authority is not an exceptionally strong argument. After all, in such cases a claim is being accepted as true simply because a person is asserting that it is true. The person may be an expert, but her expertise does not really bear on the truth of the claim. This is because the expertise of a person does not actually determine whether the claim is true or false. Hence, arguments that deal directly with evidence relating to the claim itself will tend to be stronger.

3. Appeal To Celebrity

DEFINITION: Using someone's celebrity to support a claim. This is a variant of Appeal To Authority.

EXAMPLE: "Harlan Ellison hates Lord of the Rings .  Therefore Lord of the Rings stinks."

PROOF: Show that the celebrity is not an authority.

4. Hearsay

DEFINITION: A variation of the fallacious appeal to authority is hearsay. An argument from hearsay is an argument which depends on second or third hand sources.

EXAMPLE: "Angelina Jolie doesn't like her fans because she told John Doe that she doesn't.  And John Doe said this to me!"

PROOF: Show that the source is not a direct source.

6. Appeal To Rumor

DEFINITION: A variation on the fallacy of anonymous authorities is the Appeal To Rumour. Because the source of a rumour is typically not known, it is not possible to determine whether to believe the rumour. Very often false and harmful rumours are deliberately started in order to discredit an opponent.

EXAMPLE: "Rumor has it that Michael Jackson sleeps in an oxygen tent."

PROOF: Argue that because we don't know the source of the information, we have no way to evaluate the reliability of the information.

7. Style Over Substance

DEFINITION: The manner in which an argument (or arguer) is presented is taken to affect the likelihood that the conclusion is true.  While it is true that the manner in which an argument is presented will affect whether people believe that its conclusion is true, nonetheless, the truth of the conclusion does not depend on the manner in which the argument is presented.

EXAMPLE: "This person says the Abomidable Snowman is real, and his posts are written stylishly.  He must be right."

PROOF: Show that the style in this case does not affect the truth or falsity of the conclusion.


Inductive Fallacies

Inductive reasoning consists of inferring from the properties of a sample
to the properties of a population as a whole.

An inductive argument is an argument such that the premises provide
(or appear to provide) some degree of support (but less than complete support)
for the conclusion.

No inductive inference is perfect. That means that any inductive inference can
sometimes fail. Even though the premises are true, the conclusion might be false.

The following are inductive fallacies:

1. Hasty Generalization

DEFINITION: The size of the sample is too small to support the conclusion.

EXAMPLE: "These three Southerners said bad things about black people.  Therefore all Southerners hate black people."

PROOF: Identify the size of the sample and the size of the population, then show that the sample size is too small. Note: a formal proof would require a mathematical calculation. This is the subject of probability theory. For now, you must rely on common sense.

2. Unrepresentative Sample

DEFINITION: The sample used in an inductive inference is relevantly different from the population as a whole.

EXAMPLE: "This Newsmax website had a poll, and in this poll, 80% voted that Bush is the best president.  Therefore, 80% of the world thinks Bush is the best president."  (Bush fans would be more likely to visit a Newsmax website than the general population.)

PROOF: Show how the sample is relevantly different from the population as a whole, then show that because the sample is different, the conclusion is probably different.

3. False Analogy / Extended Analogy

DEFINITION: In an analogy, two objects (or events), A and B are shown to be similar. Then it is argued that since A has property P, so also B must have property P. An analogy fails when the two objects, A and B, are different in a way which affects whether they both have property P.

EXAMPLE: "Government is like business, so just as business must be sensitive primarily to the bottom line, so also must government." (But the objectives of government and business are completely different, so probably they will have to meet different criteria.)

PROOF: Identify the two objects or events being compared and the property which both are said to possess. Show that the two objects are different in a way which will affect whether they both have that property.

4. Slothful Induction

DEFINITION: The proper conclusion of an inductive argument is denied despite the evidence to the contrary.

EXAMPLE: "Hugo has had twelve accidents n the last six months, yet he insists that it is just a coincidence and not his fault." (Inductively, the evidence is overwhelming that it is his fault.)

PROOF: About all you can do in such a case is to point to the strength of the inference.

5. Fallacy Of Exclusion

DEFINITION: Important evidence which would undermine an inductive argument is excluded from consideration. The requirement that all relevant information be included is called the "principle of total evidence".

EXAMPLE: "The Leafs will probably win this game because they've won nine out of their last ten." (Eight of the Leafs' wins came over last place teams, and today they are playing the first place team.)

PROOF: Give the missing evidence and show that it changes the outcome of the inductive argument. Note that it is not sufficient simply to show that not all of the evidence was included; it must be shown that the missing evidence will change the conclusion.


Fallacies Involving Statistical Syllogisms

A statistical generalization is a statement which is usually true, but not always true.
Thus, when an author treats a statistical generalization as though it
were always true, the author commits a fallacy.

This section describes the following fallacies involving statistical syllogisms:

1. Accident

DEFINITION: A general rule is applied when circumstances suggest that an exception to the rule should apply.

EXAMPLE: "It is good to be nice to people.  Therefore when a mugger shoots a person with a gun, you should be nice to him."

PROOF: Identify the generalization in question and show that it is not a universal generalization. Then show that the circumstances of this case suggest that the generalization ought not to apply.

2. Converse Accident / Sweeping Generalization / Dicto Simpliciter

DEFINITION: An exception to a generalization is applied to cases where the generalization should apply.  

EXAMPLE: ""Women are on average not as strong as men and less able to carry a gun. Therefore women can't pull their weight in a military unit." The problem is that the sweeping statement may be true (on average, women are indeed weaker than men), but it is not necessarily true for every member of the group in question (there are some women who are much stronger than the average).

PROOF: Identify the generalization in question and show how the special case was an exception to the generalization.


Causal Fallacies

It is common for arguments to conclude that one thing causes another.
But the relation between cause and effect is a complex one. It is easy to make a mistake.

In general, we say that a cause C is the cause of an effect E if and only if:

(i) Generally, if C occurs, then E will occur, and
(ii) Generally, if C does not occur, then E will not occur ether.

We say "generally" because there are always exceptions.

The following are causal fallacies:

1. Coincidental Correlation (post hoc ergo propter hoc ) / Non causa pro causa / False Cause
    Confusing Coincidental Relationships With Causes

DEFINITION: The fallacy of Non Causa Pro Causa occurs when something is identified as the cause of an event, but it has not actually been shown to be the cause.

A Post Hoc is a fallacy with the following form:

1. A occurs before B.
2. Therefore A is the cause of B.

The Post Hoc fallacy derives its name from the Latin phrase "Post hoc, ergo propter hoc." This has been traditionally interpreted as "After this, therefore because of this." This fallacy is committed when it is concluded that one event causes another simply because the proposed cause occurred before the proposed effect. More formally, the fallacy involves concluding that A causes or caused B because A occurs before B and there is not sufficient evidence to actually warrant such a claim.

It is evident in many cases that the mere fact that A occurs before B in no way indicates a causal relationship. For example, suppose Jill, who is in London, sneezed at the exact same time an earthquake started in California. It would clearly be irrational to arrest Jill for starting a natural disaster, since there is no reason to suspect any causal connection between the two events. While such cases are quite obvious, the Post Hoc fallacy is fairly common because there are cases in which there might be some connection between the events. For example, a person who has her computer crash after she installs a new piece of software would probably suspect that the software was to blame. If she simply concluded that the software caused the crash because it was installed before the crash she would be committing the Post Hoc fallacy. In such cases the fallacy would be committed because the evidence provided fails to justify acceptance of the causal claim. It is even theoretically possible for the fallacy to be committed when A really does cause B, provided that the "evidence" given consists only of the claim that A occured before B. The key to the Post Hoc fallacy is not that there is no causal connection between A and B. It is that adequate evidence has not been provided for a claim that A causes B. Thus, Post Hoc resembles a Hasty Generalization in that it involves making a leap to an unwarranted conclusion. In the case of the Post Hoc fallacy, that leap is to a causal claim instead of a general proposition.

Not surprisingly, many superstitions are probably based on Post Hoc reasoning. For example, suppose a person buys a good luck charm, does well on his exam, and then concludes that the good luck charm caused him to do well. This person would have fallen victim to the Post Hoc fallacy. This is not to say that all "superstitions" have no basis at all. For example, some "folk cures" have actually been found to work.

Post Hoc fallacies are typically committed because people are simply not careful enough when they reason. Leaping to a causal conclusion is always easier and faster than actually investigating the phenomenon. However, such leaps tend to land far from the truth of the matter. Because Post Hoc fallacies are committed by drawing an unjustified causal conclusion, the key to avoiding them is careful investigation. While it is true that causes proceed effects (outside of Star Trek, anyways), it is not true that precedence makes something a cause of something else. Because of this, a causal investigation should begin with finding what occurs before the effect in question, but it should not end there.

EXAMPLE: "I had a cold.  I found Jesus.  Two days later my cold was gone.  Jesus cured my cold!"

PROOF: Show that the correlation is coincidental by showing that: (i) the effect would have occurred even if the cause did not occur, or (ii) that the effect was caused by something other than the suggested cause.

2. Joint Effect

DEFINITION: One thing is held to cause another when in fact both are the effect of a single underlying cause. This fallacy is often understood as a special case of post hoc ergo prompter hoc.

EXAMPLE: "I watched a movie and didn't like it.  I also got depressed.  This proves it's a bad movie." (The real reason the person became depressed was because this person's father had died in a car wreck, and the person found out just hours before they went to the movie)

PROOF: Identify the two effects and show that they are caused by the same underlying cause. It is necessary to describe the underlying cause and prove that it causes each symptom.

3. Genuine but Insignificant Cause

DEFINITION: The object or event identified as the cause of an effect is a genuine cause, but insignificant when compared to the other causes of that event.  

EXAMPLE: "You don't support the troops? You are creating disharmony.  This is why the war isn't over."

PROOF: Identify the much more significant cause.

Note that this fallacy does not apply when all other contributing causes are equally insignificant. Thus, it is not a fallacy to say that you helped cause a movie to bomb at the box office because you refused to pay money to see it, for your refusal to pay money had as much weight as any other movie-goer, and hence is equally a part of the cause.

4. Wrong Direction

DEFINITION: The relation between cause and effect is reversed.

EXAMPLE: "People's suspicion of politicians is why many politicians are corrupt."  (Actually, it's the other way around.)

PROOF: Give a causal argument showing that the relation between cause and effect has been reversed.

5. Complex Cause

DEFINITION: The effect is caused by a number of objects or events, of which the cause identified is only a part. A variation of this is the feedback loop where the effect is itself a part of the cause.

EXAMPLE: "The Challenger explosion was caused by the cold weather." (True, however, it would not have occurred had the O-rings been properly constructed.)

PROOF: Show that all of the causes, and not just the one mentioned, are required to produce the effect.


Missing the Point

These fallacies have in common a general failure to prove that the conclusion is true.

The following fallacies are cases of missing the point:

1. Begging the Question ( petitio principii ) / Circular Reasoning

DEFINITION: The truth of the conclusion is assumed by the premises. Often, the conclusion is simply restated in the premises in a slightly different form. In more difficult cases, the premise is a consequence of the conclusion. Begging the Question is a fallacy in which the premises include the claim that the conclusion is true or (directly or indirectly) assume that the conclusion is true. This sort of "reasoning" typically has the following form.

1. Premises in which the truth of the conclusion is claimed or the truth of the conclusion is assumed (either directly or indirectly).
2. Claim C (the conclusion) is true.

This sort of "reasoning" is fallacious because simply assuming that the conclusion is true (directly or indirectly) in the premises does not constitute evidence for that conclusion. Obviously, simply assuming a claim is true does not serve as evidence for that claim. This is especially clear in particularly blatant cases: "X is true. The evidence for this claim is that X is true."

Some cases of question begging are fairly blatant, while others can be extremely subtle.

EXAMPLE: "The Bible is true because the Bible says so."

PROOF: Show that in order to believe that the premises are true we must already agree that the conclusion is true.

2. Irrelevant Conclusion ( ignoratio elenchi )

DEFINITION: An argument which purports to prove one thing instead proves a different conclusion.

EXAMPLE: "All children should have ample attention from their parents. Parents who work full-time cannot give ample attention to their children. Therefore, mothers should not work full-time."

PROOF: Show that the conclusion proved by the author is not the conclusion that the author set out to prove.

3. Straw Man

DEFINITION: The Straw Man fallacy is committed when a person simply ignores a person's actual position and substitutes a distorted, exaggerated or misrepresented version of that position. This sort of "reasoning" has the following pattern:

1. Person A has position X.
2. Person B presents position Y (which is a distorted version of X).
3. Person B attacks position Y.
4. Therefore X is false/incorrect/flawed.

This sort of "reasoning" is fallacious because attacking a distorted version of a position simply does not constitute an attack on the position itself. One might as well expect an attack on a poor drawing of a person to hurt the person.

EXAMPLE: "Senator Jones says that we should not fund the submarine program. I disagree entirely. He wants to leave us defenseless."

PROOF: Show that the opposition's argument has been misrepresented by showing that the opposition has a stronger argument. Describe the stronger argument.


Fallacies of Ambiguity

The fallacies in this section are all cases where a word or phrase is used unclearly.

There are two ways in which this can occur.

(i) The word or phrase may be ambiguous, in which case it has more than one distinct meaning.

(ii) The word or phrase may be vague, in which case it has no distinct meaning.

The following are fallacies of ambiguity:

1. Equivocation

DEFINITION: The same word is used with two different meanings.

EXAMPLE: "All banks are beside rivers. Therefore, the financial institution where I deposit my money is beside a river." (In this argument, there are two unrelated meanings of the word "bank".)

PROOF: Identify the word which is used twice, then show that a definition which is appropriate for one use of the word would not be appropriate for the second use.

2. Amphiboly

DEFINITION: An amphiboly occurs when the construction of a sentence allows it to have two different meanings.

EXAMPLE: "Last night I saw an elephant in my pajamas."  (Was he wearing the pajamas, or the elephant?)

PROOF: Identify the ambiguous phrase and show the two possible interpretations.

3. Accent

DEFINITION: Emphasis is used to suggest a meaning different from the actual content of the proposition.

EXAMPLE: "I would never suggest that BIGFOOT IS REAL!"

EXAMPLE #2: "Governor Johnson was competent this week." (This implies he may be incompetent in other weeks.)

PROOF: Identify the accent and show a more accurate way of stating the real content.


Category Errors

These fallacies occur because the author mistakenly assumes that the whole is
nothing more than the sum of its parts. However, things joined together may have
different properties as a whole than any of them do separately.

The following fallacies are category errors:

1. Composition

DEFINITION: The fallacy of Composition is committed when a conclusion is drawn about a whole based on the features of its constituents when, in fact, no justification provided for the inference. There are actually two types of this fallacy, both of which are known by the same name (because of the high degree of similarity).

The first type of fallacy of Composition arises when a person reasons from the characteristics of individual members of a class or group to a conclusion regarding the characteristics of the entire class or group (taken as a whole). More formally, the "reasoning" would look something like this.

1. Individual F things have characteristics A, B, C, etc.
2. Therefore, the (whole) class of F things has characteristics A, B, C, etc.

This line of reasoning is fallacious because the mere fact that individuals have certain characteristics does not, in itself, guarantee that the class (taken as a whole) has those characteristics.

It is important to note that drawing an inference about the characteristics of a class based on the characteristics of its individual members is not always fallacious. In some cases, sufficient justification can be provided to warrant the conclusion. For example, it is true that an individual rich person has more wealth than an individual poor person. In some nations (such as the US) it is true that the class of wealthy people has more wealth as a whole than does the class of poor people. In this case, the evidence used would warrant the inference and the fallacy of Composition would not be committed.

The second type of fallacy of Composition is committed when it is concluded that what is true of the parts of a whole must be true of the whole without there being adequate justification for the claim. More formally, the line of "reasoning" would be as follows:

1. The parts of the whole X have characteristics A, B, C, etc.
2. Therefore the whole X must have characteristics A, B, C.

That this sort of reasoning is fallacious because it cannot be inferred that simply because the parts of a complex whole have (or lack) certain properties that the whole that they are parts of has those properties. This is especially clear in math: The numbers 1 and 3 are both odd. 1 and 3 are parts of 4. Therefore, the number 4 is odd.

It must be noted that reasoning from the properties of the parts to the properties of the whole is not always fallacious. If there is justification for the inference from parts to whole, then the reasoning is not fallacious. For example, if every part of the human body is made of matter, then it would not be an error in reasoning to conclude that the whole human body is made of matter. Similiarly, if every part of a structure is made of brick, there is no fallacy comitted when one concludes that the whole structure is made of brick.

EXAMPLE: "The human body is made up of cells, which are invisible. Therefore, the body is invisible."

PROOF: Show that the properties in question are the properties of the parts, and not of the whole. If necessary, describe the parts to show that they could not have the properties of the whole.

2. Division

DEFINITION: The fallacy of Division is committed when a person infers that what is true of a whole must also be true of its constituents and justification for that inference is not provided.

There are two main variants of the general fallacy of Division:

The first type of fallacy of Division is committed when 1) a person reasons that what is true of the whole must also be true of the parts and 2) the person fails to justify that inference with the required degree of evidence. More formally, the "reasoning" follows this sort of pattern:

1. The whole, X, has properties A, B, C, etc.
2. Therefore the parts of X have properties A, B, C, etc.

That this line of reasoning is fallacious is made clear by the following case: 4 is an even number. 1 and 3 are parts of 4. Therefore 1 and 3 are even.

It should be noted that it is not always fallacious to draw a conclusion about the parts of a whole based on the properties of the whole. As long as adequate evidence is provided in the argument, the the reasoning can be acceptable. For example, the human body is made out of matter and it is reasonable to infer from this that the parts that make up the human body are also made out of matter. This is because there is no reason to believe that the body is made up of non-material parts that somehow form matter when they get together.

The second version of the fallacy of division is committed when a person 1) draws a conclusion about the properties of indvidual members of a class or group based on the collective properties of the class or group and 2) there is not enough justification for the conclusion. More formally, the line of "reasoning" is as follows:

1. As a collective, Group or class X has properties A, B, C, etc.
2. Therefore the individual members of group or class X have properties A, B, C, etc.

That this sort of reasoning is fallacious can be easily shown by the following: It is true that athletes, taken as a group, are football players, track runners, swimmers, tennis players, long jumpers, pole vaulters and such. But it would be fallacious to infer that each individual athlete is a football player, a track runner, a swimmer, a tennis player, a swimmer, etc.

It should be noted that it is not always fallacious to draw a conclusion about an individual based on what is true of the class he/she/it belongs to. If the inference is backed by evidence, then the reasoning can be fine. For example, it is not fallacious to infer that Bill the Siamese cat is a mammal from the fact that all cats are mammals. In this case, what is true of the class is also true of each individual member.

EXAMPLE: "People are made out of atoms. People are visible. Therefore, a single atom is visible."

PROOF: Show that the properties in question are the properties of the whole, and not of its parts. If necessary, describe the parts to show that they could not have the properties of the parts.


Non-Sequitur

The term non sequitur literally means "it does not follow". In this section we
describe fallacies which occur as a consequence of invalid arguments.

The following fallacies are non sequiturs:

1. Affirming the Consequent

DEFINITION: Any argument of the following form is invalid: "If A, then B.  B. Therefore, A."

EXAMPLE: "If it's raining then the streets are wet. The streets are wet. Therefore, it's raining."

PROOF: Show that even though the premises are true, the conclusion could be false. In general, show that B might be a consequence of something other than A.

2. Denying the Antecedent

DEFINITION: Any argument of the following form is invalid: "If A, then B. Not A. Therefore, Not B."

EXAMPLE: "If it's raining, then the street is wet. It isn't raining. Therefore, the street isn't wet."

PROOF: Show that even though the premises are true, the conclusion may be false. In particular, show that the consequence B may occur even though A does not occur. For example, a fire hydrant could be leaking, thus making the street wet.

3. Inconsistency

DEFINITION: The author asserts more than one proposition such that the propositions cannot all be true. In such a case, the propositions may be contradictories or they may be contraries.

EXAMPLE: "Fire came before computers.  Computers came before the internet.  Therefore the internet came before fire."

PROOF: Assume that one of the statements is true, and then use it as a premise to show that one of the other statements is false.


Syllogistic Fallacies

The fallacies in this section are all cases of invalid categorical syllogisms.

The following are syllogistic fallacies:

1. Fallacy of the Four Terms (quaternio terminorum)

DEFINITION: A standard form categorical syllogism contains four terms. When there is a flaw in the four terms, then there is a fallacy.

EXAMPLE: "No Republicans are Democrats. All conservatives are Republicans. Therefore, no conservatives are Democrats."

PROOF: Identify the four terms and where necessary state the meaning of each term.

2. Undistributed Middle

DEFINITION: The middle term in the premises of a standard form categorical syllogism never refers to all of the members of the category it describes.

EXAMPLE: "There are money-trees because money is green and so are trees, so money must grow on trees."

PROOF: Show how each of the two categories identified in the conclusion could be separate groups even though they share a common property.

3. Illicit Major

DEFINITION: The predicate term of the conclusion refers to all members of that category, but the same term in the premises refers only to some members of that category.

EXAMPLE: "All dogs are animals. No cats are dogs. Therefore, no cats are animals.."

PROOF: Show that there may be other members of the predicate category not mentioned in the premises which are contrary to the conclusion.

4. Illicit Minor

DEFINITION: The subject term of the conclusion refers to all members of that category, but the same term in the premises refers only to some members of that category.

EXAMPLE: "All whales are mammals. All mammals are animals. Therefore, all animals are whales."

PROOF: Show that there may be other members of the subject category not mentioned in the premises which are contrary to the conclusion.

5. Fallacy of Drawing an Affirmative Conclusion From a Negative Premise

DEFINITION: The conclusion of a standard form categorical syllogism is affirmative, but at least one of the premises is negative.

EXAMPLE: "All whales are mammals. Some fish are not whales. Therefore, some fish are mammals."

PROOF: Assume that the premises are true. Find an example which allows the premises to be true but which clearly contradicts the conclusion.

6. Existential Fallacy

DEFINITION: A standard form categorical syllogism with two universal premises has a particular conclusion. The idea is that some universal properties need not be instantiated.

EXAMPLE: "All unicorns are animals. Therefore, some animals are unicorns."

PROOF:  Assume that the premises are true, but that there are no instances of the category described.


Fallacies of Explanation

An explanation is a form of reasoning which attempts to answer the question "why?"
For example, it is with an explanation that we answer questions such as, "Why is Kirk a human?"

A good explanation will be based on a scientific or empirical theory.
The explanation of why Kirk is a man will be given in terms of the composition of a human, and theories of humanity.

The following are fallacies of explanation:

1. Subverted Support

DEFINITION: An explanation is intended to explain why some phenomenon happens. The explanation is fallacious if the phenomenon does not actually happen, or if there is no evidence that it does happen.

EXAMPLE: "Arabs want to destroy America because they hate democracy."

PROOF: Identify the phenomenon which is being explained. Show that there is no reason to believe that the phenomenon has actually occurred.

2. Non-Support

DEFINITION: An explanation is intended to explain who some phenomenon happens. In this case, there is evidence that the phenomenon occurred, but it is trumped up, biased or ad hoc evidence.

EXAMPLE: "The reason why most bachelors are timid is that their mothers were domineering." (This attempts to explain why most bachelors are timid. However, it is shown that the author bases his generalization on two bachelors he once knew, both of whom were timid.)

PROOF: Identify the phenomenon which is being explained. Show that the evidence advanced to support the existence of the phenomenon was manipulated in some way.

3. Untestability

DEFINITION: The theory advanced to explain why some phenomen occurs cannot be tested.

We test a theory by means of its predictions. For example, a theory may predict that a new Kirk movie would do poorly at the box office. If the predicted event fails to occur, then this is evidence against the theory.  

EXAMPLE: ""I won the lottery because my psychic aura made me win."(The way to test this theory to try it again. But the person responds that her aura worked for that one case only. There is thus no way to determine whether the win was the result of an aura of of luck.)

A theory is also untestable when it predicts events which would occur whether or not the theory were true.

EXAMPLE: "If they made a new horror movie, people would make fun of horror fans." (People would do that regardless of whether a horror movie was made.)

A theory also cannot be tested when it makes no predictions.

PROOF: Identify the theory. Show that it makes no predictions, or that it is impossible to test, or that the predictions it does make cannot ever be wrong, even if the theory is false.

4. Limited Scope

DEFINITION: The theory doesn't explain anything other than the phenomenon it explains.

EXAMPLE: "My theory is that people get schizophrenia because different parts of their brains split apart." (This theory merely explains what schizophrenia is - and nothing else.)

PROOF: Identify the theory and the phenomenon it explains. Show that the theory does not explain anything else. Argue that theories which explain only one phenomenon are likely to be incomplete, at best.

5. Limited Depth

DEFINITION: Theories explain phenomena by appealing to some underlying cause or phenomena. Theories which do not appeal to an underlying cause, and instead simply appeal to membership in a category, commit the fallacy of limited depth.

EXAMPLE: "My daughter likes President Bush because she is a daughter." (This does not explain why her daughter likes Bush, nor why any daughter would like Bush)

EXAMPLE #2: "You're just saying that because you are a Mets fan." (This attempt at dismissal tries to explain your behaviour as frivolous. However, it fails because it is not an explanation at all. Suppose every Mets fan were to say that. Then what? We have to get deeper - we have to ask why they would say that - before we can decide that what they are saying is frivolous.)

PROOF: Theories of this sort attempt to explain a phenomenon by showing that it is part of a category of similar phenomenon. Accept this, then press for an explanation of the wider category of phenomenon. Argue that a theory refers to a cause, not a classification.


Fallacies Of Definition

In order to make our words or concepts clear, we use a definition.
The purpose of a definition is to state exactly what a word means.
A good definition should enable a reader to 'pick out' instances of the word or concept with no outside help.

The following are fallacies of definition:

1. Too Broad

DEFINITION: The definition includes items which should not be included.

EXAMPLE:"Mets fans are humans who like baseball." (Braves fans are also humans who like baseball. So it is included in the definition. But obviously many Braves fans are NOT Mets fans.)

PROOF: Identify the term being defined. Identify the conditions in the definition. Find an item which meets the condition but is obviously not an instance of the term.

2. Too Narrow

DEFINITION: The definition does not include items which should be included.

EXAMPLE: "A person is a baseball fan if and only if they like the Mets." (Braves fans are baseball fans, however, they do not necessarily like the Mets. Thus they are not included in the definition, however, they should be.)

 PROOF: Identify the term being defined. Identify the conditions in the definition. Find an item which is an instance of the term but does not meet the conditions.

3. Failure to Elucidate

DEFINITION: The definition is harder to understand than the term being defined.

EXAMPLE: "The world is beautiful if and only if it is aesthetically successful." (The term "aesthetically successful" is harder to understand than the term "beautiful".)

PROOF: Identify the term being defined. Identify the conditions in the definition. Show that the conditions are no more clearly defined than the term being defined.

4. Circular Definition (Circulus in demonstrando)

DEFINITION: The definition includes the term being defined as a part of the definition.  (A circular definition is a special case of a Failure to Elucidate.)

EXAMPLE: Family Guy is sexist because it has sexist undertones. (We would need to know what "sexist" is in order to tell whether the show is "sexist".)

PROOF: Identify the term being defined. Identify the conditions in the definition. Show that at least one term used in the conditions is the same as the term being defined.

5. Conflicting Conditions

DEFINITION: The definition is self-contradictory.

EXAMPLES: "You cannot judge the Bible if you DO read it, because if you read it that means you must like it.  And you cannot judge the Bible if you do NOT read it, because if you haven't read it you don't know what you're talking about." (This implies you cannot judge the Bible regardless of whether you read it or not.)

PROOF: Identify the conditions in the definition. Show that they cannot all be true at the same time (in particular, assume that one of the conditions is true, then show from this that another of the conditions must be false).


Other Fallacies

These fallacies are also extremely important to recognize and point out, but
I have not put them in a category yet.  They are still VERY important.

1. Appeal to Tradition / Argumentum ad antiquitatem / Appeal to the Old or Past or Age

DEFINITION: Appeal to Tradition is a fallacy that occurs when it is assumed that something is better or correct simply because it is older, traditional, or "always has been done." The opposite of Argumentum ad Novitatem.

This sort of "reasoning" has the following form:

1. X is old or traditional
2. Therefore X is correct or better.

This sort of "reasoning" is fallacious because the age of something does not automatically make it correct or better than something newer. This is made quite obvious by the following example: The theory that witches and demons cause disease is far older than the theory that microrganisms cause diseases. Therefore, the theory about witches and demons must be true.

This sort of "reasoning" is appealing for a variety of reasons. First, people often prefer to stick with what is older or traditional. This is a fairly common psychological characteristic of people which may stem from the fact that people feel more comfortable about what has been around longer. Second, sticking with things that are older or traditional is often easier than testing new things. Hence, people often prefer older and traditional things out of laziness. Hence, Appeal to Tradition is a somewhat common fallacy.

It should not be assumed that new things must be better than old things (see the fallacy Appeal to Novelty) any more than it should be assumed that old things are better than new things. The age of something does not, in general, have any bearing on its quality or correctness (in this context). In the case of tradition, assuming that something is correct just because it is considered a tradition is poor reasoning. For example, if the belief that 1+1 = 56 were a tradition of a group of people it would hardly follow that it is true.

Obviously, age does have a bearing in some contexts. For example, if a person concluded that aged wine would be better than brand new wine, he would not be committing an Appeal to Tradition. This is because, in such cases the age of the thing is relevant to its quality. Thus, the fallacy is committed only when the age is not, in and of itself, relevant to the claim.

One final issue that must be considered is the "test of time." In some cases people might be assuming that because something has lasted as a tradition or has been around a long time that it is true because it has "passed the test of time." If a person assumes that something must be correct or true simply because it has persisted a long time, then he has committed an Appeal to Tradition. After all, as history has shown people can persist in accepting false claims for centuries.

However, if a person argues that the claim or thing in question has successfully stood up to challenges and tests for a long period of time then they would not be committing a fallacy. In such cases the claim would be backed by evidence. As an example, the theory that matter is made of subatomic particles has survived numerous tests and challenges over the years so there is a weight of evidence in its favor. The claim is reasonable to accept because of the weight of this evidence and not because the claim is old. Thus, a claim's surviving legitimate challenges and passing valid tests for a long period of time can justify the acceptance of a claim. But mere age or persistance does not warrant accepting a claim.

EXAMPLE: "John is older than his son, therefore he is better."

PROOF: Show that older does not always mean better.

2. Argumentum Ad Novitatem / Appeal To The New / Appeal To Novelty / Newer Is Better

DEFINITION: Appeal to Novelty is a fallacy that occurs when it is assumed that something is better or correct simply because it is new.

This sort of "reasoning" has the following form:

1. X is new.
2. Therefore X is correct or better.

This sort of "reasoning" is fallacious because the novelty or newness of something does not automatically make it correct or better than something older. This is made quite obvious by the following example: Joe has proposed that 1+1 should now be equal to 3. When asked why people should accept this, he says that he just came up with the idea. Since it is newer than the idea that 1+1=2, it must be better.

This sort of "reasoning" is appealing for many reasons. First, "western culture" includes a very powerful committment to the notion that new things must be better than old things. Second, the notion of progress (which seems to have come, in part, from the notion of evolution) implies that newer things will be superior to older things. Third, media advertising often sends the message that newer must be better. Because of these three factors (and others) people often accept that a new thing (idea, product, concept, etc.) must be better because it is new. Hence, Novelty is a somewhat common fallacy, escpecially in advertising.

It should not be assumed that old things must be better than new things (see the fallacy Appeal to Tradition) anymore than it should be assumed that new things are better than old things. The age of thing does not, in general, have any bearing on its quality or correctness (in this context).

Obviously, age does have a bearing in some contexts. For example, if a person concluded that his day old milk was better than his two-month old milk, he would not be committing an Appeal to Novelty. This is because, in such cases the newness of the thing is relevant to its quality. Thus, the fallacy is committed only when the newness is not, in and of itself, relevant to the claim.

EXAMPLE: "Bill is a younger than his father, therefore he is better."

PROOF: Point out that newer does not always mean better.

3. Argumentum ad crumenam

DEFINITION: This is the fallacy of believing that money is a criterion of correctness; that those with more money are more likely to be right. The opposite of Argumentum ad Lazarum.

EXAMPLE: "Britney Spears gets paid a lot more money than you, so she must be a better parent than you."

PROOF: Point out that richer does not always mean better.

4. Argumentum ad Lazarum

DEFINITION: This is the fallacy of believing that a LACK of money is a criterion of correctness; that those with less money are more likely to be right.

EXAMPLE: "I am not some rich Hollywood type, I am a simple man with a modest salary.  Therefore I know more about how children should be raised than a rich Hollywood person like Andy Griffith."

PROOF: Point out that poorer does not always mean better.

5. Argumentum ad logicam

DEFINITION: This is the "fallacy fallacy" of arguing that a proposition is false because it has been presented as the conclusion of a fallacious argument. Remember always that fallacious arguments can arrive at true conclusions.

EXAMPLE:

Tom: "All cats are animals. Ginger is an animal. This means Ginger is a cat.".
Bill: "Ah you just committed the affirming the consequent logical fallacy. Sorry, you are wrong, which means that Ginger is not a cat".

PROOF: Point out that just because there was a fallacy in the logic, that it does not make the conclusion incorrect.

6. Argumentum ad nauseam

DEFINITION: This is the incorrect belief that an assertion is more likely to be true, or is more likely to be accepted as true, the more often it is heard. So an Argumentum ad Nauseam is one that employs constant repetition in asserting something; saying the same thing over and over again until you're sick of hearing it.

EXAMPLE: "Liberals are traitors." (repeated over and over again, even though there is no merit to this statement whatsoever.)

PROOF: Point out that repeating a statement over and over does not make the statement true.

7. Audiatur et altera pars

DEFINITION: Often, people will argue from assumptions which they don't bother to state. The principle of Audiatur et Altera Pars is that all of the premises of an argument should be stated explicitly. It's not strictly a fallacy to fail to state all of your assumptions; however, it's often viewed with suspicion.

PROOF: Ask the person how he came to the assumption.

8. The Natural Law fallacy / Appeal to Nature

DEFINITION: The Appeal to Nature is a common fallacy in political arguments. One version consists of drawing an analogy between a particular conclusion, and some aspect of the natural world -- and then stating that the conclusion is inevitable, because the natural world is similar. Another form of appeal to nature is to argue that because human beings are products of the natural world, we must mimic behavior seen in the natural world, and that to do otherwise is 'unnatural'.

EXAMPLE: "People shouldn't try to stay healthy.  People die.  It's just human nature."

9. The "No True Scotsman..." fallacy

DEFINITION: This is the flawed logic in the "No True Scotsman..." fallacy:

a. Show me a Scotsman that puts sugar on his porridge.

b. No true Scotsman puts sugar on his porridge.

c. Thus, anyone who puts sugar on his porridge is not a true Scotsman.

d. Therefore, you cannot show me a true Scotsman that puts sugar on his porridge.

As you can see, this game is rigged.

This is an example of an ad hoc change being used to shore up an assertion, combined with an attempt to shift the meaning of the words used original assertion; you might call it a combination of fallacies.

PROOF: Point out the fallacies in their statements and ask them to redefine.

10. Plurium interrogationum / Many questions

DEFINITION: This fallacy occurs when someone demands a simple (or simplistic) answer to a complex question.

EXAMPLE: "Is the universe cold? Yes or no?"

PROOF: Point out that the question is too complex to be answered with a simple answer.  Sometimes offering a more complex answer will solve the problem.

11. Red Herring / Smoke Screen / Wild Goose Chase

DEFINITION: This fallacy is committed when someone introduces irrelevant material to the issue being discussed, so that everyone's attention is diverted away from the points made, towards a different conclusion.  The basic idea is to "win" an argument by leading attention away from the argument and to another topic.

This sort of "reasoning" has the following form:

1. Topic A is under discussion.
2. Topic B is introduced under the guise of being relevant to topic A (when topic B is actually not relevant to topic A).
3. Topic A is abandoned.

This sort of "reasoning" is fallacious because merely changing the topic of discussion hardly counts as an argument against a claim.

EXAMPLE: "You claim that Bigfoot isn't real. But aren't dogs real?"

PROOF: Point out the Red Herring and ask them to refocus back to the subject at hand (and clarify the original point, in case anyone had gotten lost).

12. Reification / Hypostatization

DEFINITION: Reification occurs when an abstract concept is treated as a concrete thing.

EXAMPLE: "The Government wants to tell you what to do." This assumes government is a being with desires.

PROOF: Point out that an abstract concept cannot be treated as if it were a concrete thing.

13. Appeal To Ridicule / Appeal to Mockery / The Horse Laugh / Humor

DEFINITION: The Appeal to Ridicule is a fallacy in which ridicule or mockery is substituted for evidence in an "argument." And/or using inappropriate humor or ridicule to avoid the issue, to cast unwarranted aspersions, or to deflect attention away from the discussion.

This line of "reasoning" has the following form:

1. X, which is some form of ridicule is presented (typically directed at the claim).
2. Therefore claim C is false.

This sort of "reasoning" is fallacious because mocking a claim does not show that it is false. This is especially clear in the following example: "1+1=2! That's the most ridiculous thing I have ever heard!"

It should be noted that showing that a claim is ridiculous through the use of legitimate methods (such as a non fallacious argument) can make it reasonable to reject the claim. One form of this line of reasoning is known as a "reductio ad absurdum" ("reducing to absurdity"). In this sort of argument, the idea is to show that a contradiction (a statement that must be false) or an absurd result follows from a claim. For example: "Bill claims that a member of a minority group cannot be a racist. However, this is absurd. Think about this: white males are a minority in the world. Given Bill's claim, it would follow that no white males could be racists. Hence, the Klan, Nazis, and white supremists are not racist organizations."

Since the claim that the Klan, Nazis, and white supremists are not racist organizations is clearly absurd, it can be concluded that the claim that a member of a minority cannot be a racist is false.

EXAMPLE: "You say that one plus one equals two?  Don't make me laugh!  You made me spill coffee from laughing so hard!  How silly such a statement is!  LOL!!!"

PROOF: Point out the ridicule and that it will not deflect attention away from the discussion, nor will casting unwarranted aspersions prove something as true.

14. Stolen Concept

DEFINITION: One or more concepts on which an argument logically depends are denied in the argument.

EXAMPLE: "I do not exist. "

PROOF:
In putting forth his argument the author both accepts and denies the same proposition, (though usually not explicitly) thus accepts contradictory positions. This is essentially the same as Aristotle's "reaffirmation through denial".

15. Bandwagon / peer pressure / ostracism

DEFINITION: Appeals to the need for belonging.  The Bandwagon is a fallacy in which a threat of rejection by one's peers (or peer pressure) is substituted for evidence in an "argument." This line of "reasoning" has the following form:

1. Person P is pressured by his/her peers or threatened with rejection.
2. Therefore person P's claim X is false.

This line of "reasoning" is fallacious because peer pressure and threat of rejection do not constitute evidence for rejecting a claim. This is expecially clear in the following example:

EXAMPLE:

Joe: "Bill, I know you think that 1+1=2. But we don't accept that sort of thing in our group. "
Bill: "I was just joking. Of course I don't believe that."

It is clear that the pressure from Bill's group has no bearing on the truth of the claim that 1+1=2.

It should be noted that loyalty to a group and the need to belong can give people very strong reasons to conform to the views and positions of those groups. Further, from a practical standpoint we must often compromise our beliefs in order to belong to groups. However, this feeling of loyalty or the need to belong simply do not constitute evidence for a claim.

PROOF: Point out that jumping on the bandwagon will not change the facts.

16. Fallacy Of Opposition

DEFINITION: Stating that a person must be wrong for no reason other than their conclusions differ from yours.

EXAMPLE: "You don't like spinach, like I do?  Well, you don't have an open mind like me, then."

PROOF: Point out that just because a person has come to a different conclusion than theirs, does not mean the person is wrong.

17. Guilt By Association

DEFINITION: Attacking the idea because of those who support it, or make spurious links between publicly favorable things and publicly unfavorable things.

EXAMPLE: "You support the ACLU?  So do pedophiles!"

PROOF: Point out that just because you support the same goal, does not mean you do the same things that some others in that group have done.

18. Nothing But Objections

DEFINITION: Continually raising objections as a means of avoiding the issue.

EXAMPLE: "Why do I not like John?  I don't like what he does.  The things he does bother me.  I hate what he does."

PROOF: Point out that repeated objections are doing nothing but avoiding the issue.  Refocus on the real issue.

19. Rationalization

DEFINITION: Making excuses instead of addressing the issue.

EXAMPLE: "That's not what I meant!"

PROOF: Get them to refocus on the real issue.

20. Ad lapidem

DEFINITION: Dismissing a statement as absurd or false without demonstrating it to be such.

EXAMPLE: "You say that my business only made $1 last year?  That's not true!  I don't care what the numbers say!  It's absurd!" (They do not state why it is not true.)

PROOF: As them to demonstrate why they feel the statement is false or absurd.

21. Lip service

DEFINITION: Verbal agreement or declaration unsupported in action or true conviction.

EXAMPLE: "I like John, but I think he's worthless." (Their actions and their declaration are polar opposites)

PROOF: Point out how their declarations are unsupported by their actions.

22. Relativist Fallacy / Subjectivist Fallacy

DEFINITION: Asserting that because there are no applicable objective truths, the truthfulness of a proposition is grounded in the respective perceptions of each individual or group.

The Relativist Fallacy is committed when a person rejects a claim by asserting that the claim might be true for others but is not for him/her. This sort of "reasoning" has the following form:

1. Claim X is presented.
2. Person A asserts that X may be true for others but is not true for him/her.
3. Therefore A is justified in rejecting X.

In this context, relativism is the view that truth is relative to Z (a person, time, culture, place, etc.). This is not the view that claims will be true at different times or of different people, but the view that a claim could be true for one person and false for another at the same time.

In many cases, when people say "that X is true for me" what they really mean is "I believe X" or "X is true about me." It is important to be quite clear about the distinction between being true about a person and being true for a person. A claim is true about a person if the claim is a statement that describes the person correctly. For example, "Bill has blue eyes" is true of Bill if Bill has blue eyes. To make a claim such as "X is true for Bill" is to say that the claim is true for Bill and that it need not be true for others. For example: "1+1=23 is true for Bill" would mean that, for Bill, 1+1 actually does equal 23, not that he merely believes that 1+1=23 (that would be "It is true of Bill that he believes 1+1=23"). Another example would be "The claim that the earth is flat is true for Bill" would mean that the earth really is flat for Bill (in other words, Bill would be in a different world than the rest of the human race). Since these situations (1+1 being 23 and the earth being flat for Bill) are extremely strange, it certainly seems that truth is not relative to individuals (although beliefs are).

As long as truth is objective (that is, not relative to individuals), then the Relativist Fallacy is a fallacy. If there are cases in which truth is actually relative, then such reasoning need not be fallacious.

23. Overprecision

DEFINITION: Rejecting a concept as unusable because it has borderline cases or because the definition, phrasing, syntax, grammar, or structure of the proposition or argument is not perfect.

EXAMPLE: "Your post is too long and is full of grammatical errors. And you typed in ALL CAPS.  Therefore your comments are useless."

PROOF: Point out that minor imperfections on irrelevent elements does not alter the facts.

24. Personification

DEFINITION: Attributing human traits to other creatures or reading purpose into inanimate configurations.

EXAMPLE: "The set design looked tired in this episode.  Therefore the episode was tired."

PROOF: Point out that that the non-human is not a human.  Ask them to explain it in more logical terms.

25. Quoting out of context

DEFINITION: Manipulating a quote either from an authority, or from one's opponent, in such a way that the original meaning of the statement is altered.

EXAMPLE: "Einstein said 'god' in a writing. Therefore he was religious." (This quote is out-of-context and is not showing the feelings the author originally intended.)

PROOF: Point out that the quote has been manipulated, and illustrate the full context of the quote (even better if you do so after asking THEM to do so, and they refuse or make excuses.)

26. Wicked alternative

DEFINITION: Attempting to support one proposition by denouncing another, when the second is not opposite of the first.

EXAMPLE: "I may say mean things about Sally, but at least I don't trash her entire family!" (this does not make what he IS doing justifiable)

PROOF: Point out that the "lesser of the two evils" does not make it any less incorrect.

27. Fallacy of the beard

DEFINITION: That you cannot come to a conclusion because one thing differs from another only in degree. (The name of the fallacy derives from the difficulty of determining when exactly someone has a beard).

EXAMPLE: "When did Lincoln really have a beard?  Is it when one has a `five-o'clock shadow'? When the whiskers are one quarter of an inch long? Longer? Just when is one's facial hair long enough to be called a beard? Just because one cannot determine how long the hair has to be does not mean that three inches of facial hair cannot be called a beard, and a slight stubble should not. "

PROOF: Point out that just because the line is hard to draw does not mean that differences mean nothing.

28. Vague Similarities

DEFINITION: Asserting that two situations or existants are similar without specifying the properties they share.

EXAMPLE:"Hitler and Clinton are more alike than you may think." (They do not specify how they are similar.)

PROOF: Point out that they need to be more specific on how they came to their conclusion of similarity.  Pointing out differences can also help.

29. Reductio Ad Absurdum

DEFINITION: The reductio ad absurdum ("reduction to absurdity") is an argument form which works backward from an absurd conclusion to show that a premise of the argument must be false.

EXAMPLE: a. Nothing can do what is physically impossible.  
                    b. It is physically impossible for Tom to walk.
                    c. Therefore, Tom cannot walk.

                    However, Tom can, in fact, walk. Therefore, either premise a or b must be false (in this case, premise b).

PROOF: Point out the fallacy, and their flawed premise(s).

30. Appeal To Common Practice

DEFINITION: The Appeal to Common Practice is a fallacy with the following structure:

1. X is a common action.
2. Therefore X is correct/moral/justified/reasonable, etc.

The basic idea behind the fallacy is that the fact that most people do X is used as "evidence" to support the action or practice. It is a fallacy because the mere fact that most people do something does not make it correct, moral, justified, or reasonable.

An appeal to fair play, which might seem to be an appeal to common practice, need not be a fallacy. For example, a woman working in an office might say "the men who do the same job as me get paid more than I do, so it would be right for me to get paid the same as them." This would not be a fallacy as long as there was no relevant difference between her and the men (in terms of ability, experience, hours worked, etc.). More formally:

1. It is common practice to treat people of type Y in manner X and to treat people of type Z in a different manner.
2. There is no relevant difference between people of type Y and type Z.
3. Therefore people of type Z should be treated in manner X, too.

This argument rests heavily on the principle of relevant difference. On this principle two people, A and B, can only be treated differently if and only if there is a relevant difference between them. For example, it would be fine for me to give a better grade to A than B if A did better work than B. However, it would be wrong of me to give A a better grade than B simply because A has red hair and B has blonde hair.

There might be some cases in which the fact that most people accept X as moral entails that X is moral. For example, one view of morality is that morality is relative to the practices of a culture, time, person, etc. If what is moral is determined by what is commonly practiced, then this argument:

1. Most people do X.
2. Therefore X is morally correct.

would not be a fallacy. This would however entail some odd results. For example, imagine that thereare only 100 people on earth. 60 of them do not steal or cheat and 40 do. At this time, stealing and cheating would be wrong. The next day, a natural disaster kills 30 of the 60 people who do not cheat or steal. Now it is morally correct to cheat and steal. Thus, it would be possible to change the moral order of the world to one's view simply by eliminating those who disagree.

31. Questionable Cause

DEFINITION: This fallacy has the following general form:

1. A and B are associated on a regular basis.
2. Therefore A is the cause of B.

The general idea behind this fallacy is that it is an error in reasoning to conclude that one thing causes another simply because the two are associated on a regular basis. More formally, this fallacy is committed when it is concluded that A is the cause of B simply because they are associated on a regular basis. The error being made is that a causal conclusion is being drawn from inadequate evidence.

The Questionable Cause Fallacy is actually a general type of fallacy. Any causal fallacy that involves an error in a reasoning due to a failure to adequately investigate the suspected cause is a fallacy of this type. Thus, fallacies like Post Hoc and Confusing Cause and Effect are specific examples of the general Questionable Cause Fallacy.

Causal reasoning can be quite difficult since causation is a rather complex philosophic issue. The complexity of causation is briefly discussed in the context of the specific versions of this fallacy.

The key to avoiding the Questionable Cause fallacy is to take due care in drawing causal conclusions. This requires taking steps to adequately investigate the phenomena in question as well using the proper methods of careful investigation.

32. Appeal to Consequences of a Belief / Wishful Thinking

DEFINITION: The Appeal to the Consequences of a Belief is a fallacy that comes in the following patterns:

1. X is true because if people did not accept X as being true then there would be negative consequences.
2. X is false because if people did not accept X as being false, then there would be negative consequences.

3. X is true because accepting that X is true has positive consequences.
4. X is false because accepting that X is false has positive consequences.

5. I wish that X were true, therefore X is true. This is known as Wishful Thinking.
6. I wish that X were false, therefore X is false. This is known as Wishful Thinking.

This line of "reasoning" is fallacious because the consequences of a belief have no bearing on whether the belief is true or false. For example, if someone were to say "If sixteen-headed purple unicorns don't exist, then I would be miserable, so they must exist" it would be clear that this would not be a good line of reasoning. It is important to note that the consequences in question are the consequences that stem from the belief. It is important to distinguish between a rational reason to believe evidence that objectively and logically supports the claim, and a reason to accept the belief because of some external factor (such as fear, a threat, or a benefit or harm that may stem from the belief) that is relevant to what a person values but is not relevant to the truth or falsity of the claim.

The nature of the fallacy is especially clear in the case of Wishful thinking. Obviously, merely wishing that something is true does not make it true. This fallacy differs from the Appeal to Belief fallacy in that the Appeal to Belief involves taking a claim that most people believe that X is true to be evidence for X being true.

33. Appeal to Flattery / Apple Polishing

This has other "colorful" terms like brownnosing, *sskissing, etc.

An Appeal to Flattery is a fallacy of the following form:

1. Person A is flattered by person B.
2. Person B makes claim X.
3. Therefore X is true.

The basic idea behind this fallacy is that flattery is presented in the place of evidence for accepting a claim. this sort of "reasoning" is fallacious because flattery is not, in fact, evidence for a claim. This is especially clear in a case like this: "My Bill, that is a really nice tie. By the way, it is quite clear that one plus one is equal to forty three."

34. Appeal To Spite

The Appeal to Spite Fallacy is a fallacy in which spite is substituted for evidence when an "argument" is made against a claim. This line of "reasoning" has the following form:

1. Claim X is presented with the intent of generating spite.
2. Therefore claim C is false (or true)

This sort of "reasoning" is fallacious because a feeling of spite does not count as evidence for or against a claim. This is quite clear in the following case: "Bill claims that the earth revolves around the sun. But remember that dirty trick he pulled on you last week. Now, doesn't my claim that the sun revolves around the earth make sense to you?"

Of course, there are cases in which a claim that evokes a feeling of spite or malice can serve as legitimate evidence. However, it should be noted that the actual feelings of malice or spite are not evidence. The following is an example of such a situation:

Jill: "I think I'll vote for Jane to be treasurer of NOW."
Vicki: "Remember the time that your purse vanished at a meeting last year?"
Jill: "Yes."
Vicki:"Well, I just found out that she stole your purse and stole some other stuff from people."
Jill: "I'm not voting for her!"

In this case, Jill has a good reason not to vote for Jane. Since a treasurer should be honest, a known thief would be a bad choice. As long as Jill concludes that she should vote against Jane because she is a thief and not just out of spite, her reasoning would not be falacious.

35. Spotlight

DEFINITION: The Spotlight fallacy is committed when a person uncritically assumes that all members or cases of a certain class or type are like those that receive the most attention or coverage in the media. This line of "reasoning" has the following form:

1. Xs with quality Q receive a great deal of attention or coverage in the media.
2. Therefore all Xs have quality Q.

This line of reasoning is fallacious since the mere fact that someone or something attracts the most attention or coverage in the media does not mean that it automatically represents the whole population. For example, suppose a mass murderer from Old Town, Maine received a great deal of attention in the media. It would hardly follow that everyone from the town is a mass murderer.

The Spotlight fallacy derives its name from the fact that receiving a great deal of attention or coverage is often referred to as being in the spotlight. It is similar to Hasty Generalization, Biased Sample and Misleading Vivideness because the error being made involves generalizing about a population based on an inadequate or flawed sample.

The Spotlight Fallacy is a very common fallacy. This fallacy most often occurs when people assume that those who receive the most media attention actually represent the groups they belong to. For example, some people began to believe that all those who oppose abortion are willing to gun down doctors in cold blood simply because those incidents received a great deal of media attention. Since the media typically covers people or events that are unusual or exceptional, it is somewhat odd for people to believe that such people or events are representative.

For brief discussions of adequate samples and generalizations, see the entries for Hasty Generalization and Biased Sample.

36. Biased Sample / Biased Statistics / Loaded Sample / Prejudiced Statistics
      Prejudiced Sample / Loaded Statistics / Biased Induction / Biased Generalization

DEFINITION: This fallacy is committed when a person draws a conclusion about a population based on a sample that is biased or prejudiced in some manner. It has the following form:

1. Sample S, which is biased, is taken from population P.
2. Conclusion C is drawn about Population P based on S.

The person committing the fallacy is misusing the following type of reasoning, which is known variously as Inductive Generalization, Generalization, and Statistical Generalization:

1. X% of all observed A's are B''s.
2. Therefore X% of all A's are Bs.

The fallacy is committed when the sample of A's is likely to be biased in some manner. A sample is biased or loaded when the method used to take the sample is likely to result in a sample that does not adequately represent the population from which it is drawn.

Biased samples are generally not very reliable. As a blatant case, imagine that a person is taking a sample from a truckload of small colored balls, some of which are metal and some of which are plastic. If he used a magnet to select his sample, then his sample would include a disproportionate number of metal balls (after all, the sample will probably be made up entirely of the metal balls). In this case, any conclusions he might draw about the whole population of balls would be unreliable since he would have few or no plastic balls in the sample.

The general idea is that biased samples are less likely to contain numbers proportional to the whole population. For example, if a person wants to find out what most Americans thought about gun control, a poll taken at an NRA meeting would be a biased sample.

Since the Biased Sample fallacy is committed when the sample (the observed instances) is biased or loaded, it is important to have samples that are not biased making a generalization. The best way to do this is to take samples in ways that avoid bias. There are, in general, three types of samples that are aimed at avoiding bias. The general idea is that these methods (when used properly) will result in a sample that matches the whole population fairly closely. The three types of samples are as follows

Random Sample: This is a sample that is taken in such a way that nothing but chance determines which members of the population are selected for the sample. Ideally, any individual member of the population has the same chance as being selected as any other. This type of sample avoids being biased because a biased sample is one that is taken in such a way that some members of the population have a significantly greater chance of being selected for the sample than other members. Unfortunately, creating an ideal random sample is often very difficult.

Stratified Sample: This is a sample that is taken by using the following steps: 1) The relevant strata (population subgroups) are identified, 2) The number of members in each stratum is determined and 3) A random sample is taken from each stratum in exact proportion to its size. This method is obviously most useful when dealing with stratified populations. For example, a person's income often influences how she votes, so when conducting a presidential poll it would be a good idea to take a stratified sample using economic classes as the basis for determining the strata. This method avoids loaded samples by (ideally) ensuring that each stratum of the population is adequately represented.

Time Lapse Sample: This type of sample is taken by taking a stratified or random sample and then taking at least one more sample with a significant lapse of time between them. After the two samples are taken, they can be compared for changes. This method of sample taking is very important when making predictions. A prediction based on only one sample is likely to be a Hasty Generalization (because the sample is likely to be too small to cover past, present and future populations) or a Biased Sample (because the sample will only include instances from one time period).

People often commit Biased Sample because of bias or prejudice. For example, a person might intentionally or unintentionally seek out people or events that support his bias. As an example, a person who is pushing a particular scientific theory might tend to gather samples that are biased in favor of that theory.

People also commonly commit this fallacy because of laziness or sloppiness. It is very easy to simply take a sample from what happens to be easily available rather than taking the time and effort to generate an adequate sample and draw a justified conclusion.

It is important to keep in mind that bias is relative to the purpose of the sample. For example, if Bill wanted to know what NRA members thought about a gun control law, then taking a sampleat a NRA meeting would not be biased. However, if Bill wanted to determine what Americans in general thought about the law, then a sample taken at an NRA meeting would be biased.

37. Questionable Cause / Confusing Cause and Effect

Confusing Cause and Effect is a fallacy that has the following general form:

1. A and B regularly occur together.
2. Therefore A is the cause of B.

This fallacy requires that there is not, in fact, a common cause that actually causes both A and B.

This fallacy is committed when a person assumes that one event must cause another just because the events occur together. More formally, this fallacy involves drawing the conclusion that A is the cause of B simply because A and B are in regular conjunction (and there is not a common cause that is actually the cause of A and B). The mistake being made is that the causal conclusion is being drawn without adequate justification.

In some cases it will be evident that the fallacy is being committed. For example, a person might claim that an illness was caused by a person getting a fever. In this case, it would be quite clear that the fever was caused by illness and not the other way around. In other cases, the fallacy is not always evident. One factor that makes causal reasoning quite difficult is that it is not always evident what is the cause and what is the effect. For example, a problem child might be the cause of the parents being short tempered or the short temper of the parents might be the cause of the child being problematic. The difficulty is increased by the fact that some situations might involve feedback. For example, the parents' temper might cause the child to become problematic and the child's behavior could worsen the parents' temper. In such cases it could be rather difficult to sort out what caused what in the first place.

In order to determine that the fallacy has been committed, it must be shown that the causal conclusion has not been adequately supported and that the person committing the fallacy has confused the actual cause with the effect. Showing that the fallacy has been committed will typically involve determining the actual cause and the actual effect. In some cases, as noted above, this can be quite easy. In other cases it will be difficult. In some cases, it might be almost impossible. Another thing that makes causal reasoning difficult is that people often have very different conceptions of cause and, in some cases, the issues are clouded by emotions and ideologies. For example, people often claim violence on TV and in movies must be censored because it causes people to like violence. Other people claim that there is violence on TV and in movies because people like violence. In this case, it is not obvious what the cause really is and the issue is clouded by the fact that emotions often run high on this issue.

While causal reasoning can be difficult, many errors can be avoided with due care and careful testing procedures. This is due to the fact that the fallacy arises because the conclusion is drawn without due care. One way to avoid the fallacy is to pay careful attention to the temporal sequence of events. Since (outside of Star Trek), effects do not generally precede their causes, if A occurs after B, then A cannot be the cause of B. However, these methods go beyond the scope of this program.

All causal fallacies involve an error in causal reasoning. However, this fallacy differs from the other causal fallacies in terms of the error in reasoning being made. In the case of a Post Hoc fallacy, the error is that a person is accepting that A is the cause of B simply because A occurs before B. In the case of the Fallacy of Ignoring a Common Cause A is taken to be the cause of B when there is, in fact, a third factor that is the cause of both A and B. For more information, see the relevant entries in this program.

38. Special Pleading

DEFINITION: Special Pleading is a fallacy in which a person applies standards, principles, rules, etc. to others while taking herself (or those she has a special interest in) to be exempt, without providing adequate justification for the exemption. This sort of "reasoning" has the following form:

1. Person A accepts standard(s) S and applies them to others in circumtance(s) C.
2. Person A is in circumstance(s) C.
3. Therefore A is exempt from S.

The person committing Special Pleading is claiming that he is exempt from certain principles or standards yet he provides no good reason for his exemption. That this sort of reasoning is fallacious is shown by the following extreme example:

1. Barbara accepts that all murderers should be punished for their crimes.
2. Although she murdered Bill, Barbara claims she is an exception because she really would not like going to prison.
3. Therefore, the standard of punishing murderers should not be applied to her.

This is obviously a blatant case of special pleading. Since no one likes going to prison, this cannot justify the claim that Barbara alone should be exempt from punishment.

From a philosophic standpoint, the fallacy of Special Pleading is violating a well accepted principle, namely the Principle of Relevant Difference. According to this principle, two people can be treated differently if and only if there is a relevant difference between them. This principle is a reasonable one. After all, it would not be particularly rational to treat two people differently when there is no relevant difference between them. As an extreme case, it would be very odd for a parent to insist on making one child wear size 5 shoes and the other wear size 7 shoes when the children are both size 5.

It should be noted that the Principle of Relevant Difference does allow people to be treated differently. For example, if one employee was a slacker and the other was a very prodictive worker the boss would be justified in giving only the productive worker a raise. This is because the productive of each is a relevant difference between them. Since it can be reasonable to treat people differently, there will be cases in which some people will be exempt from the usual standards. For example, if it is Bill's turn to cook dinner and Bill is very ill, it would not be a case of Special Pleading if Bill asked to be excused from making dinner (this, of course, assumes that Bill does not accept a standard that requires people to cook dinner regardless of the circumstances). In this case Bill is offering a good reason as to why he should be exempt and, most importantly, it would be a good reason for anyone who was ill and not just Bill.

While determing what counts as a legitimate basis for exemption can be a difficult task, it seems clear that claiming you are exempt because you are you does not provide such a legitimate basis. Thus, unless a clear and relevant justification for exemption can be presented, a person cannot claim to be exempt.

There are cases which are similar to instances of Special Pleading in which a person is offering at least some reason why he should be exempt but the reason is not good enough to warrant the exemption. This could be called "Failed Pleading." For example, a professor may claim to be exempt from helping the rest of the faculty move books to the new department office because it would be beneath his dignity. However, this is not a particularly good reason and would hardly justify his exemption. If it turns out that the real "reason" a person is claiming exemption is that they simply take themselves to be exempt, then they would be committing Special Pleading. Such cases will be fairly common. After all, it is fairly rare for adults to simply claim they are exempt without at least some pretense of justifying the exemption.

39. Two Wrongs Make A Right

DEFINITION: Two Wrongs Make a Right is a fallacy in which a person "justifies" an action against a person by asserting that the person would do the same thing to him/her, when the action is not necessary to prevent B from doing X to A. This fallacy has the following pattern of "reasoning":

1. It is claimed that person B would do X to person A.
2.It is acceptable for person A to do X to person B (when A's doing X to B is not necessary to prevent B from doing X to A).
3. This sort of "reasoning" is fallacious because an action that is wrong is wrong even if another person would also do it.

It should be noted that it can be the case that it is not wrong for A to do X to B if X is done to prevent B from doing X to A or if X is done in justified retribution. For example, if Sally is running in the park and Biff tries to attack her, Sally would eb jsutified in attacking Biff to defend herself. As another example, if country A is planning to invade country B in order to enslave the people, then country B would be justified in launching a pre-emptive strike to prevent the invasion.


FALSE PROOFS:

Proof by example:

The author gives only the case n=2 and suggests that it contains most of the ideas of the general proof.

Proof by intimidation:

'Trivial.'

Proof by vigorous handwaving:

Works well in a classroom or seminar setting.

Proof by cumbersome notation:

Best done with access to at least four alphabets and special symbols.

Proof by exhaustion:

An issue or two of a journal devoted to your proof is useful.

Proof by omission:

'The reader may easily supply the details.'

'Look it up on Google, I don't have time to provide the evidence myself.'

'The other 253 cases are analogous.'

'...'

Proof by obfuscation:

A long plotless sequence of true and/or meaningless syntactically related statements.

Proof by wishful citation:

The author cites the negation, converse, or generalization of a theorem from the literature to support his claims.

Proof by funding:

How could three different government agencies be wrong?

Proof by eminent authority:

'I saw Karp in the elevator and he said it was probably NP-complete.'

Proof by personal communication:

'Eight-dimensional colored cycle stripping is NP-complete' [Karp, personal commmunication].

Proof by reduction to the wrong problem:

'To see that infinite-dimensional colored cycle stripping is decidable, we reduce it to the halting problem.'

Proof by reference to inaccessible literature:

The author cites a simple corollary of a theorem to be found in a privately circulated memoir of the Slovenian Philological Society, 1883.

Proof by importance:

A large body of useful consequences all follow from the proposition in question.

Proof by accumulated evidence:

Long and diligent search has not revealed a counterexample.

Proof by cosmology:

The negation of the proposition is unimaginable or meaningless. Popular for proofs of the existence of God.

Proof by mutual reference:

In reference A, Theorem 5 is said to follow from Theorem 3 in reference B, which is shown to follow from Corollary 6.2 in reference C, which is an easy consequence of Theorem 5 in reference A.

Proof by metaproof:

A method is given to construct the desired proof. The correctness of the method is proved by any of these techniques.

Proof by picture:

A more convincing form of proof by example. Combines well with proof by omission.

Proof by vehement assertion:

It is useful to have some kind of authority relation to the audience.

Proof by ghost reference:

Nothing even remotely resembling the cited theorem appears in the reference given.

Proof by forward reference:

Reference is usually to a forthcoming paper of the author, which is often not as forthcoming as at first.

Proof by semantic shift:

Some standard but inconvenient definitions are changed for the statement of the result.

Proof by appeal to intuition:

Cloud-shaped drawings frequently help here.



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