Logical Fallacies (non sequiturs) (partial list)

I. Fallacies of Ambiguity

1. Begging the question (petitio principii): to employ circular reasoning by using one's conclusion (in a disguised form) as a premise.

2. Complex or Leading Question: a question that is phrased in such a way that it cannot be answered without granting some particular answer to some point at issue. (E.g. "Are you still beating your wife?")

3. Accident (fallacia accidentis): improperly applying a generalization or general principle to a particular instance. This is the opposite of the hasty or sweeping generalization (see II., 3, below).

4. Continuum or "Argument of the Beard" (as in, "exactly how many whiskers must a man have before he can be said to have a beard?"): an attempt to establish that the existence of a gradual continuum between extremes is proof against any real difference between them, because there is no absolute dividing line.

5. Bad Analogy: an attempt to equate two things when only a superficial similarity exists. This is refutable by reductio ad absurdum (reducing the analogy to a patent absurdity merely by extending the line of reasoning).

6. Post hoc, ergo propter hoc (after this, therefore because of this): to infer causality from mere temporal priority. (Just because one event happened before another does not mean that the first event caused the second one.)

7. Composition: an argument that a property which is affirmed or denied of every part of some whole must also be affirmed or denied of the whole. (E.g. the affirmation that since all members of the Catholic Church (on earth) are sinners, therefore the Catholic Church is sinful is a fallacy of composition. The truth is that the Church, being the Bride of Christ and the Mystical Body of Christ, is a sinless society by the promise of Christ and the agency of the Holy Spirit, despite the fact that all her members remain sinners.)

8. Division: the opposite of composition; an argument that a property which is affirmed or denied of a whole must also be affirmed or denied of each of its constituent parts. (E.g. it is fallacious to affirm that, since the Church is infallible in matters of faith and morals, each one of Her members must also be likewise personally infallible. This fallacy is employed by the "We Are Church" crowd.)

9. Equivocation (equivocatio or homonymia): playing upon the double meaning of a term in a misleading or erroneous fashion.

10. Amphiboly: A sentence with a built-in ambiguity due to its peculiar structure is said to be amphibolous. The fallacy of amphiboly is committed when the amphibolous structure of a sentence is played upon in a misleading or erroneous fashion.

11. Accent: Sometimes a sentence takes on different meanings as it is accented in different ways. The fallacy of accent is committed when a false or misleading inference is made from a sentence which is improperly accented (i.e. some of its terms are unnecessarily stressed) when the same sentence, when properly accented, is perfectly true and clear.


II. Irrelevant Appeals

Aristotle identified fallacies that were committed by people who were ignorant of the question at issue. These fallacies are classified in general as ignorantio elenchi, ignorant refutations, that is to say, the person committing them either proves the wrong point or he arrives at his conclusion by a set of premises irrelevant to the point at issue, or both. With the exception of the hasty generalization, these are informal fallacies, i.e. they do not necessarily involve a formal mistake in logic, they are merely irrelevant.

1. Abusing the Man (argumentum ad hominem, arguing to the man; as opposed to arguing ad rem, to the point): there are at least four basic types:
a. Name-calling
b. "Let's-play-amateur-psychoanalyst" (calling into question the opponent's mental health)
c. Casting aspersions on the opponent's moral character
d. Poisoning the wells (an attempt to discredit the opponent absolutely, to destroy his reliability for anything in the eyes of the audience).

2. Argumentum ad populum (appeal to the people or popular sentiments): there are three main types:
a. Argumentum ad captandum vulgas (appeal to the emotions of the crowd)
b. Argumentum ad invidium (appeal to the prejudices of one's audience)
c. Argumentum ad misericordiam (appeal to the pity or sympathy of one's audience)

3. Hasty (or Sweeping) Generalization: This is committed when, after observing that a small number or a special sort of the members of some group have some property, it is then inferred that the whole group has this property. One must not draw unnecessary conclusions or make a judgment about a large population on the basis of an observation of certain members of that population who have very special positions or functions or who happen to be in extraordinary or atypical situations.

4. Shifting the Burden of Proof: The burden of proof properly rests on the proponent, the one making the assertion; the opponent has no obligation to disprove the assertion or to prove the contrary. The proponent commits a logical error if he tries to force the opponent to prove the assertion to be false when he has not adequately proven it to be true.

5. Special Pleading: citing only those facts which seem to support one's position while avoiding those which seem to undermine it. Logic requires a proponent to consider all of the pertinent facts. Special pleading misrepresents the proponent's case by excluding any facts which might damage it.

6. Red Herring: an attempt to divert attention away from the topic at hand by bringing up side-issues or subtly changing the subject altogether.

7. Straw Man: This is a misrepresentation--a caricature--of one's opponent's position, which the proponent sets up so as to easily knock it down. Since a straw man is not an accurate statement of the opponent's position, what the proponent is actually attacking is not the true position at all, but a figment of his own imagination.

8. False Antithesis, Faulty Dilemma or False Dichotomy: assuming two options to be opposite and/or mutually exclusive when such might not actually be the case. There may be more than two options and/or they may not be opposed to each other, but rather complementary aspects of a unified truth. This fallacy is the flip-side of the "argument of the beard" (continuum). Both demand an absolute division between positions which may not in fact exist.

9. Argumentum ad ignorantiam (appealing to the ignorance of the opponent or audience): basing one's argument on some field of expertise of which one presumes the opponent or audience is ignorant--very dangerous if the proponent is himself ignorant of it.

10. Misuse of Authority, or argumentum ad verecundiam (argument to modesty or bashfulness-because the proponent is attempting to hide behind some authority rather than letting his own reasoning or evidence stand subject to evaluation or scrutiny): This fallacy is related to the argumentum ad ignorantiam. One must first understand the nature and use of authority and its overall context, as well as the limitations of any single authority, or the attempt to use it may backfire in fallacy.

11. Appeal to Force (Argumentum ad baculum): This is committed when a proponent attempts to sway an opponent to accept his view by applying some real or imagined threat of force or violence. Although the appeal to force is, logically speaking, irrelevant, it is often persuasive nonetheless.

12. Cliché Thinking: "the lazy man's guide to truth;" clichés and truisms, however convenient and appropriate in casual discourse, cannot substitute for sound reasoning and must not be the basis of one's argument or point of view.

13. Chronological Snobbery: to imply in one's argument that an idea that is old is therefore no longer true; a basis for the heresy called "Modernism."

14. Hypothesis Contrary to Fact: to base one's argument on a hypothetical situation, "what might have been." "If only…" and "what if…" statements cannot serve as valid premises.