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Argument by Adjective


A speaker may pepper his argument with adjectives (or adverb), adding unproved assertions. This tactic draws attention away from the main argument, and as such is a form of red herring. Since the assertions have not been developed, refuting them may be difficult as well. Even if the speaker using them has not met his burden of proof, the emotional content of the adjective.

For instance, an activist or lobbyist may say, "There will be serious repercussions from this illegal bill, and I don't just mean to the political fortunes of those who hypocritically voted for it."

What "serious" means in this context is left veiled, but the real gem is "illegal", which presupposes a number of conditions. Illegality implies some (higher) authority whose precepts have been countermanded, but the bare adjective doesn't specify who that authority is, or in what way the law violates those (higher) precepts. Again, that those who voted for some law professed not to want it is left undeveloped, but the charge of "hypocrisy" raises distrust.

I'll look for other examples and update them here.

Straw Man


A Straw Man argument is one that attempts to refute a position an opponent hasn't actually taken. Typically the straw man will be an extreme position or, as Bruce Thompson notes, an alleged hidden agenda.

Sometimes the straw man is simply the result of a misinterpreted position. But no matter how well the straw man is defeated, the true position remains unassailed. The Straw Man can be seen therefor as shifting the burden of proof.

Bruce Thompson:

The argument misrepresents a position that it seeks to refute. By refuting the position as misrepresented, the argument creates the impression that it has refuted the position that is actually held by opponents.
Fallacy Files:
As the "straw man" metaphor suggests, the counterfeit position attacked in a Straw Man argument is typically weaker than the opponent's actual position, just as a straw man is easier to defeat than a flesh-and-blood one. Of course, this is no accident, but is part of what makes the fallacy tempting to commit, especially to a desperate debater who is losing an argument.

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Poison the Well

Poisoning the Well is an argumentum ad hominem in which an opponent is criticized before his argument has been heard. It is fallacy of relevance, since it doesn't address the argument (being only a guess at it) but the arguer.

Bruce Thompson:

...it is not so much aimed at persuading the audience that the opponent's view is false (which would be an argument) as it is aimed at getting the audience to refuse to listen to the opponent's argument in the first place.

Fallacy Files:
The phrase "poisoning the well" ultimately alludes to the medieval European myth that the black plague was caused by Jews poisoning town wells—a myth which was used as an excuse to persecute Jews.

The Golden Mean

Wizard [Web]

The Golden Mean fallacy says that the truth is somewhere between the extremes, especially right in the middle. Rather, the truth is the truth, extreme or not; "yes" and "no" are two extremes, but very often one is correct and the other incorrect.

Begging the Question

Wizard Web
Latin: Petitio Principii

Begging the Question is circular logic in which an essential premise to the conclusion is itself, stated without support. It has nothing to do with begging for a question, as in common misuse. The "question" is the matter or subject at hand, and the "begging" can be thought of a metaphorical attempt to get it for free. The Latin petitio principii with the English cognate "petitioning the principle" is more appropriate but less colorful.

Circular Reasoning

Wizard [Web]

Latin: circulus in demonstrando, circulus in probando

Circular logic is relying on a proposition for one of its premises.

Fallacy Files:

For an argument to have any epistemological or dialectical force, it must start from premisses already known or believed by its audience, and proceed to a conclusion not known or believed. This, of course, rules out the worst cases of Begging the Question, when the conclusion is the very same proposition as the premiss, since one cannot both believe and not believe the same thing. A viciously circular argument is one with a conclusion based ultimately upon that conclusion itself, and such arguments can never advance our knowledge.

All circular logic is not Begging the Question, but used fallaciously the terms are effectively synonymous. If a premise is not truly needed to establish a proposition, then its circular nature reinforces rather than fools. Use with care, if only because an unscrupulous opponent may charge circularity.

Circular logic is not always fallacious. For instance, we know that 2 + 2 = 4 in part because 4 - 2 = 2.

The best use of circular logic, however, is indirect: if in reasoning back to our premises we encounter a contradiction, reductio ad absurdum alerts us to an error somewhere, either in our reasoning or premises. Care must be exercised here as well, because we may not find an error but still have a false conclusion. Something external to the loop must validate it, and nothing must invalidate it.

Non Causa Pro Causa

This is the generalized 'cause and effect' error. A good explanation is provided at Fallacy Files, which separates Non Causa Pro Causa into two classes of errors, based on events and types.

We can and often do mistake coincidence for cause and effect when looking at events. However, two events happening even repeatedly in the same relation to one another in time or space may be caused by some third event of which we aren't aware. We can also get the cause and effect reversed. The cause we identify may be only the end of a domino chain of causes and effects. And the events actually may be totally unrelated except in the way we observe them.

We can also mistakenly assume that because one event of type C generally causes another event of type E, that a particular event c caused a given event e. For instance, we know that shooting a gun can cause a wound, but that doesn't mean that Johnny shooting his gun caused Freddy's wound, even if they were in the same vicinity at the time of Johnny's gunshot. Someone else could have shot Freddy, Johnny may have been shooting at Freddy's assailant (so that Freddy's wound was the cause of Johnny's shot), or Freddy's wound may not even be a gunshot wound.

Cum Hoc Ergo Propter Hoc - "with this, therefore because of this"
Post Hoc Ergo Propter Hoc - "after this, therefore because of this"
Texas Sharpshooter - assuming a cluster of data points must have a cause

Shifting the Burden of Proof

Shifting the Burden of Proof is employed in two ways: by an arguer, to more easily establish a claim, and by an audience, to make it more difficult.

When employed by an arguer, too much of the conclusion is assumed, rather than being established. A special case is when (all or part of) the conclusion itself is assumed and used as a premise in the argument, which is called circular reasoning or Begging the Question.

When employed by an audience, the burden is set impossibly high. An arguer may be told that he must have a solid case proved before he can plead it.

Questions over where the burden of proof belongs (outside the legal system, which has explicit rules about it) can be easily answered with the question, "Who needs to be convinced?"

Argumentum ad hominem

Latin for: Argument at the man

An "ad hominem" attack is one against a person or group who has stated an idea, rather than the idea itself. Usually, an argumentum ad hominem is attacking a source or authority for information.

As Fallacy Files says, "Argumentum ad hominem also occurs when someone's arguments are discounted merely because they stand to benefit from the policy they advocate."

An argument can be valid or invalid no matter who makes it. A special case of this general principle is that in court, known perjurers may have an impossibly difficult burden of proof to carry, and in fact their testimony may be ruled inadmissible, especially if the perjury occurs during the case at hand.

Ad hominem arguments may often be restated in better form, as changing "You're a socialist." into "What you have expressed is socialist dogma." It still needs work, since there may not be a clear relationship between the former ad hominem target's words and socialist dogma, and there is a need to overcome the burden of proving socialist dogma to be invalid, since some may find socialist dogma to be wholly reasonable.

A special case of ad hominem is the ad hominem tu quoque, in which an argument is attacked because its proponents fail (or failed in the past) to show full adherence to it themselves.

[Updated 7/15/07 for formatting, conversion to search links, and the like.]

Appeal to Humor

Philosophy Pages


Bruce Thompson:
Any stand-up comic will tell you that the secret to humor is: tell the truth. A good comic tells us things about ourselves that we normally wouldn't want to hear since they are too embarrassing or sensitive. But by getting us to laugh at the truth about ourselves, we learn to recognize our own foibles, and we learn to forgive the foibles of others. Humor is the ultimate defense mechanism. We laugh at human foibles because this allows us to live with them. Laughter is a natural and healthy way to respond when we recognize that someone has offered us a bravely-spoken, but possibly uncomfortable, truth.

But as Thompson notes, not all things that are funny are necessarily true. Humor that exploits stereotypes may make us laugh despite knowing, or even because we know, that the stereotype is inaccurate. They transfer us to the realm of fantasy where stereotypes and magic both work, so we are allowed to laugh or feel awe over things which would otherwise be rejected by better judgement.

Julia Nefsky wrote in Philosophy Now that logical errors in humor can be the essence of the joke, enhance the humor, or be the mechanism for it. Thompson's distinction between laughing at and with the user of the illogic can appear in any of those cases.


Amphiboly (Web) is creating an ambiguous premise with poor or misleading grammatical construction.

Philosophy Pages has a great example.

Bruce Thompson:

The argument depends upon an ambiguity in grammar. One meaning makes one of the premisses true, but it makes another of the premisses false. The alternative meaning makes the second premiss true, but makes the first premiss false.

Fallacy Files suggests that typically the ambiguity is in abuse of pronouns or descriptors that could apply to either the subject or the object in a sentence.

Complex Question

Wizard, Web

Latin: Plurium Interrogationum

Philosophy Pages

The fallacy of complex question presupposes the truth of its own conclusion by including it implicitly in the statement of the issue to be considered...

Fallacy Files picks apart a Mark Crispin Miller use of the complex question, in which he makes several charges in the form of questions, each of which presupposes a damning premise.

No evidence is given in the article for any of these claims. Loaded questions are used in this way to slip claims into rhetoric without the burden of proving them, or the necessity of taking responsibility for unproven assertions.

Red Herring

A Red Herring is a proposition within an argument that seems to apply to the topic at hand, but is actually unrelated. Arguments which rely on a red herring may be perfectly sound, but can reach only an Irrelevant Conclusion. They are a subclass of (and almost synonymous with) Ignoratio Elenchi, or fallacies of relevance.

Bruce Thompson:

The speaker introduces a new subject into the discussion that has a superficial similarity to the topic under discussion. The new subject is so emotionally charged that people cannot resist arguing about it, even though it is off the original subject. Raising the new topic does not really serve the goal of bringing the original subject to a conclusion (i.e. of getting the audience to accept the speaker's position). Rather, it distracts attention away from the original subject, preventing either side from supporting its conclusion.

Fallacy Files:
This fallacy is often known by the Latin name Ignoratio Elenchi, which translates as "ignorance of refutation". The ignorance involved is either ignorance of the conclusion to be refuted—even deliberately ignoring it—or ignorance of what constitutes a refutation, so that the attempt misses the mark.
(The name of this fallacy comes from the sport of fox hunting in which a dried, smoked herring, which is red in color, is dragged across the trail of the fox to throw the hounds off the scent. Thus, a "red herring" argument is one which distracts the audience from the issue in question through the introduction of some irrelevancy.)

Appeal to Rugged Individualism

This fallacy was named by Bruce Thompson:

The argument attempts to support a position by appealing to the opinion of a small (but opinionated) group of people, or even of a single person. The presumed authority of this person or group comes from their willingness to stand alone against majority opinion.

It can be seen as an appeal to Emotion, Authority, or Novelty.

Reductio Ad Absurdum

Reduction to the Absurd
Proof By Contradiction

Reductio ad absurdum is sometimes used fallaciously, using a poorly constructed chain of reasoning from the target proposition. It is itself a perfectly good technique, being an application of the hypothetical syllogistic form

If A, then B.
Not B.
Therefore, not A.

A → B
Not B
∴ Not A
... where B includes a chain of one or more items. Any argument may be explored to find resulting contradictions which, the reasoning being valid, show one or more of the premises to be false.

The fallacious uses of reductio ad absurdum come about by using weak or fallacious reasoning as proposition B.

Philosophy Pages
A method of proving that a proposition must be false [or true] by assuming the truth [or falsity] of the proposition and then showing that this assumption, taken together with other premises whose truth is already established, would lead to a contradiction (or, at least, to an obvious falsehood). This method is sometimes called indirect proof.

Fallacy of Division

The Fallacy of Division (Wizard, Web) occurs when applying a general rule about a whole object to its component parts. For instance, supposing that because the US exports corn and soybeans, all States in the US export corn and soybeans.

Fallacy Files:

Some properties are such that, if a whole object has the property, then all of its parts will, too—for example, invisibility. However, not all properties are like this—for instance, visibility. Let's call a property which distributes from a whole object to each of its parts a "dissective" property, using Nelson Goodman's term. If P is a dissective property, then the argument form above is validating, by definition of what such a property is. However, if P is not dissective, then the argument form is non-validating, and any argument of that form commits the fallacy of Division.

Sibling Fallacy: Composition


Questia defines syllogisms quite well.

Every syllogism is a sequence of three propositions such that the first two imply the third, the conclusion. There are three basic types of syllogism: hypothetical, disjunctive, and categorical.

The rest of this post expounds on their entry.


The hypothetical syllogism, modus ponens, has as its first premise a conditional hypothesis:

If P then Q. P. Therefore, Q.

P → Q
∴ Q


The disjunctive syllogism, modus tollens, has as its first premise a statement of alternatives. If one of them can be found not to be true, then the other must be true.

Either P or Q. Not Q. Therefore, P.
P or Q
Not Q
∴ P

The categorical syllogism comprises three categorical propositions, which must be statements of the form :

Aall S are PS
Eno S is PS P
Isome S is P
Osome S is not PP

A term is said to be distributed when it refers to all members of the denoted class. "A term in a categorical proposition is distributed if and only if the proposition implies every proposition that results from replacing the term with a more specific term." -- Fallacy Files. The term S is distributed in "all S are P" and "no S is P". [ See Fallacy Files]
A categorical syllogism contains precisely three terms:
  • the major term, which is the predicate of the conclusion
  • the minor term, the subject of the conclusion
  • the middle term, which appears in both premises but not in the conclusion

Thus: All philosophers are men (middle term); all men are mortal; therefore, All philosophers (minor term) are mortal (major term). The premises containing the major and minor terms are named the major and minor premises, respectively. Aristotle noted five basic rules governing the validity of categorical syllogisms:
  1. The middle term must be distributed at least once
  2. A term distributed in the conclusion must be distributed in the premise in which it occurs
  3. Two negative premises imply no valid conclusion
  4. If one premise is negative, then the conclusion must be negative
  5. Two affirmatives imply an affirmative

Philosophy Pages has another introduction.
Bruce Thompson has a nice table.

Appeal to Authority

Latin: argumentum ad verecundiam

An Appeal to Authority is the general name for any argument that rests on who provides some evidence, rather than on the content of the evidence. The name also refers to the specific practice of citing expert opinion.

There are some matters for which an appeal to an expert is perfectly reasonable. If faced with a task of carpentry, mathematics, or bureaucracy, one is wise to consult an expert and trust the guidance received.

In informal logic, however, the opinion of an expert is seldom conclusive in itself. It may be appropriate to list expert opinion as evidence, but only after establishing that such opinion is relevant, available, trustworthy, and not contradicted by other experts, simple experimentation, or common sense. The key question to ask is: is this opinion falsifiable? The carpenter or mathematician cannot afford to give bad advice, since the quality of their advice will become apparent with use. The fortune teller or political pundit ... not so much.

The trustworthiness of an expert must also be considered with respect to the burden of proof. That is, to the extent that an argument rests on the opinion of the expert, the argument also rests on the level of respect that expert commands to the listener. As a special case, the believability of an expert varies inversely with an audience's perception of his bias relative to his opinion.

Conversely, to show that an Appeal to Authority is fallacious (or at least to counter it), it is only necessary to show that one of the following:

  • The opinion is taken out of context or misquoted
  • This or another expert has given contradictory opinions on the same subject
  • The expert is a crackpot (ad hominem versus ad verecundiam is a draw)
  • Actual facts or simple, solid reasoning that controvert the opinion
See also Experts Agree and the Zone of Conflict

Bruce Thompson:
Ad verecundiam is a Latin phrase that actually means "(appeal) to modesty." However, it is generally referred to as "Appeal to Authority." The arguments in this family appeal to the modesty, i.e. lack of knowledge or expertise, of the listener (and also generally of the speaker). Since the listener is too modest to claim to be an expert in the subject under discussion, the speaker attempts to settle the question by citing the authority of someone who is an expert.
Thompson lists these as examples of ad verecundiam:

Experts Agree and the Zone of Conflict

The "scientific consensus" on a given topic cannot be trusted. The very fact that it is appealed to as consensus, and not settled fact, should serve as a warning that weakens, rather than strengthens, an argument. What the consensus of experts does do is to set the Burden of Proof on the one who would either strengthen or challenge the consensus.

There is a fallacy hidden by the legitimate workings of the research process, making it difficult to spot: a combined Appeal to Authority and Appeal to Popularity. But a chain of two fallacies is still fallacious. The number and reputation of learned people who believe a proposition may affect how an idea spreads, but popularity does not affect truth or falsehood, particularly when the experts did not arrive at their opinions independently but were themselves relying on the authority of others in the field.

In a court of law, for instance, the truth is not determined by the number of experts one can line up to agree, else the better-funded or organized side would always win. It is up to the experts to present evidence, based on their experience and knowledge. The other side counters with expert evidence of its own, and the judge or jury evaluate. It is not the number of experts that decide the case, but the quality of the arguments each side can present. If a hundred experts declare that day is dark and night is light, the judges should find with one opposing expert noting the time and pointing to an open window.

Scientific Fact and the Zone of Conflict

Similarly, scientific belief is not, or should not be, formed on the basis of the number of scientists who believe one way or another.

All science is by definition unproven on some level; each fact is only accepted, not proved in the sense that a mathematician or logician proves something. For example, we don't know the speed of light, or that momentum is always conserved, and so on, only that according to observation and reasoning based on all of our observations to date, that the accepted fact or principle is reliable. Scientists speak of 'facts', but always with the knowledge that these 'facts' can be challenged. Challenging accepted facts requires supplying evidence and reasoning to counter them. It does not mean arranging a vote on the matter.

Experts on a given topic argue about it. The breadth of their discussion on a given topic varies, usually trending from the fundamental to the esoteric with the time and depth of study applied to the topic.

The number and reputation of scientists who accept something as probable or as fact only indicates the approximate parameters of the debate that surround a given idea. This can be thought of as the Zone of Conflict, the area for a given topic outside of which the facts are largely settled among experts. New evidence, or new arguments about old evidence, can change the popularity of a proposition, and thus expand or contract the Zone of Conflict in the field of study which pertains to that proposition, but they do not change its truth or falsehood.

Exaggerated Conflict

There is a fallacy lurking underneath the 'experts agree' layer and the 'scientific fact' layer, by which some seek to discredit a scientist or lay person based on how close his ideas are to Zone of Conflict. Conversely, some like to point out that no fact is ever totally proved, and thereby invent a controversy of fact when none really exists. Stating that all things are uncertain does not challenge a fact, any more than asserting a fact makes it so.

It is an Appeal to Ignorance to claim that because of the existence of the Zone of Conflict, any claim about that topic is as likely to be true as any other. But it is an Appeal to Authority and abuse of the Burden of Proof to claim that an argument is invalid because it is outside the Zone. In general, the range of discussion that takes place on a topic says nothing about the validity of a particular argument or the truth of a particular proposition.

Since the Burden of Proof is on the one making the assertion, it is the responsibility of the one who would expand the Zone of Conflict to show that a real question exists. Conversely, properly rebuffing such an attempt requires actually showing that the matter is settled and why the question is no longer open.

(Adapted from The Inescapable Logic of Global Warming)

Appeal to Emotion

Latin: argumentum ad populam

Philosophy Pages

The informal fallacy of persuading someone to accept (or reject) a conclusion by arousing favorable (or unfavorable) emotions toward it or by emphasizing its widespread acceptance (or rejection) by others.

Bruce Thompson says emotional appeals are fallacious when not relevant to the subject at hand. However, an emotional appeal may be directly relevant and still lead to a false conclusion, depending on whether the facts which engender the emotions are true or not.

Fallacy Files makes a distinction between relevant and fallacious appeals to emotion based on the distinction between arguments for action and for belief:
Appeals to emotion are always fallacious when intended to influence our beliefs, but they are sometimes reasonable when they aim to motivate us to act. The fact that we desire something to be true gives not the slightest reason to believe it, and the fact that we fear something being true is no reason to think it false; but the desire for something is often a good reason to pursue it, and fear of something else a good reason to flee.


Burden of Proof

The burden of proof is always on the assertion. That is, to the degree that an argument rests on some premise, to complete the argument requires establishing the premise. Failing to take on the burden of proof will mean convincing only those who already agree.

One can assume a premise as obvious, and the relative importance of that premise to the argument is the degree to which the argument employs the fallacy of Begging the Question or circular reasoning.

In most cases, we use informal logic (in essays or scientific writing) to convince the reader of some case we are building. To convince all readers, we must be sure that all readers accept all of our premises, or we dismiss those readers who do not accept our premises.

Some assumed premises are left unstated: if the world continues to revolve, if the area of a circle really does equal πr2, and so on. Depending on audience, subject matter, skill of the arguer, and how important a premise is to an argument, it may be left unstated or it may require extensive proof, or anything in between.

In political or theological debates, it is quite common for an argument to be built on an entire unstated framework of belief. Here again, to complete the argument requires establishing the premises.

See also Shifting the Burden


[this page is under heavy construction]

Logical fallacies are statements which have the look of arguments, but miss the mark by being off-topic, incomplete, or by employing some trick of language. They are categorized at PhilosophyPages this way: