A List of Fallacies In Logic

LOGICAL FALLACIES

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A fallacy is a deceptive, false, or misleading argument, notion, belief, etc.

ACCENTUS: A Fallacy of Ambiguity, where the ambiguity arises from the emphasis (accent) placed on a word or phrase.
AFFIRMATION OF THE CONSEQUENT: An argument from the truth of a hypothetical statement, and the truth of the consequent to the truth of the antecedent. In the syllogism below, P is the antecedent and Q is the consequent:

P implies Q
Q is true <-- Affirming the consequent
Therefore: P is true

AMBIGUITY: An argument in the course of which at least one term is used in different senses. Also known as equivocation. There are several types of "fallacies of ambiguity," including REIFICATION, EQUIVOCATION, AMPHIBOLY, COMPOSITION, DIVISION, and ACCENTUS.
AMPHIBOLY: A type of Fallacy of Ambiguity where the ambiguity involved is of an "amphibolous" (equivocal, uncertain) nature. Amphiboly is a syntactic error. The fallacy is caused by faulty sentence structure, and can result in a meaning not intended by the author. "The department store now has pants for men with 32 waists." (How many waists do you have? I have only one!)
APPEAL TO IGNORANCE: See ARGUMENTUM AD IGNORANTIAM
APPEAL TO TRADITION: See ARGUMENTUM AD POPULUM
ARGUMENTUM AD ANTIQUITAM: A fallacy of asserting that something is right or good simply because it is old; that is, because "that's the way it's always been."
ARGUMENTUM AD BACULUM: An argument that resorts to the threat of force to cause the acceptance of the conclusion. Ad baculum arguments also include threats of fear to cause acceptance (e.g., "Do this or you'll go to Hades when you die!" or "Might makes right.").
ARGUMENTUM AD CRUMENAM: Fallacy of believing that money is a criterion of correctness; that those with more money are more likely to be right.
ARGUMENTUM AD HOMINEM: An argument that attempts to disprove the truth of what is asserted by attacking the speaker rather than the speaker's argument. Another way of putting it: Fallacy where you attack someone's character instead of dealing with salient issues. There are two basic types of ad hominem arguments: (1) abusive, and (2) circumstantial.
ARGUMENTUM AD IGNORANTIAM: An argument that a proposition is true because it has not been shown to be false, or vice versa. Ad ignorantium arguments are also known as "appeals to ignorance." This fallacy has two forms:

P is true, because it has not been proven false.
P is false, because it has not been proven true.

ARGUMENTUM AD LAZARUM: A fallacy of assuming that because someone is poor he or she is sounder or more virtuous than one who is wealthier. This fallacy is the opposite of the informal fallacy "argumentum ad crumenam."
ARGUMENTUM AD MISERICORDIAM: An argument that appeals to pity for the sake of getting a conclusion accepted.
ARGUMENTUM AD NAUSEUM: The incorrect belief that an assertion is more likely to be true the more often it is heard. An "argumentum ad nauseum" is one that employs constant repetition in asserting a truth.
ARGUMENTUM AD NOVITAM: A fallacy of asserting that something is more correct simply because it is new or newer than something else. Or that something is better because it is newer. This type of fallacy is the opposite of the "argumentum ad antiquitam" fallacy.
ARGUMENTUM AD NUMERAM: A fallacy that asserts that the more people who support or believe a proposition then the more likely that that proposition is correct; it equates mass support with correctness.
ARGUMENTUM AD POPULUM: An argument that appeals to the beliefs of the multitude (i.e., the "populace"). Another way of putting it: Speaker deals with passions of audience rather than with salient issues. This fallacy is also known as "Appeal to Tradition" Ad populum arguments often occur in (1) propaganda, (2) demagoguery, and (3) advertising.
ARGUMENTUM AD VERECUNDIAM: An argument in which an authority is appealed to on matters outside his/her field of authority. "Ad verecundiam" also refers to a fallacy of simply resorting to appeals to authority.
BEGGING THE QUESTION:: An argument that assumes as part of its premises the very conclusion that is supposed to be true. Another way of saying this is: Fallacy of assuming at the onset of an argument the very point you are trying to prove. The fallacy is also sometimes referred to as "Circulus in Probando." This Fallacy is also known by the Latin "PETITIO PRINCIPII". The argument assumes its conclusion is true but DOES NOT SHOW it to be true. It has two forms:

P is true, because P is true.
P is true, because A is true. And A is true because B is true. And B is true because P is true.

BIFURCATION: Also referred to as the "black and white" fallacy, bifurcation is the presentation of a situation or condition with only two alternatives, whereas in fact other alternatives exist or can exist.
CIRCULAR REASONING: See "Begging the Question".
CIRCULUS IN PROBANDO: See "Begging the Question".
COMPOSITION: An argument in which one assumes that a whole has a property solely because its various parts have that property. Composition is a type of Fallacy of Ambiguity .
CONVERTING A CONDITIONAL: If P then Q, therefore, if Q then P.
CUM HOC ERGO PROPTER HOC: A and B occurred simultaneously, therefore A and B are related. A fallacy of correlation that links events because they occur simultaneously; one asserts that because two events occur together they are causally related, and leaves no room for other factors that may be the cause(s) of the events. This fallacy is similar to the "post hoc ergo propter hoc" fallacy.
CONFUSION OF CORRELATION AND CAUSATION: See Cum Hoc Ergo Propter Hoc
DENIAL OF THE ANTECEDENT: An argument in which one infers the falsity of the consequent from the truth of a hypothetical proposition, and the falsity of its antecedent.

P implies Q
Not-P
Therefore: Not-Q

DICTO SIMPLICITER: See Sweeping Generalization
DIVISION: An argument in which one assumes that various parts have a property solely because the whole has that same property. Division is a type of Fallacy of Ambiguity.
ENUMERATION OF FAVORABLE CIRCUMSTANCES: See OBSERVATIONAL SELECTION
EXCLUDED MIDDLE: See FALSE DICHOTOMY
EQUIVOCATION: An argument in which an equivocal expression is used in one sense in one premise and in a different sense in another premise, or in the conclusion. Equivocal means (1) of uncertain significance; not determined, and (2) having different meanings equally possible. Equivocation is a type of Fallacy of Ambiguity. The opposite of equivocation is "unovocation," in which a word always carries the same meaning through a given context. Equivocation is a type of Fallacy of Ambiguity.
FALSE ANALOGY: An analogy is a partial similarity between the like features of two things or events on which a comparison can be made. A false analogy involves comparing two things that are NOT similar. Note that the two things may be similar in superficial ways, but not with respect to what is being argued.
FALSE DICHOTOMY: Also called 'Excluded Middle' - considering only the two extremes in a continuum of intermediate possibilities. (e.g., If you're not part of the solution, you are part of the problem).
HASTY GENERALIZATION: An argument in which a proposition is used as a premise without attention given to some obvious condition that would affect the proposition's application. This fallacy is also known as the "hasty generalization." It is a fallacy that takes evidence from several, possibly unrepresentative, cases to a general rule; generalizing from few to many. Note the relation to statistics: Much of statistics concerns whether or not a sample is representative of a larger population. The larger the sample size, the better the representativeness. Note also that the opposite of a hasty generalization is a sweeping generalization.
HYPOSTATIZATION: See REIFICATION
IGNORATIO ELENCHI: An argument that is supposed to prove one proposition but succeeds only in proving a different one. Ignoratio elenchi stands for "pure and simple irrelevance."
ILLICIT PROCESS: A syllogistic argument in which a term is distributed in the conclusion, but not in the premises. One of the rules for a valid categorical syllogism is that if either term is distributed in the conclusion, then it must be distributed in the premises. There are two types of Illicit Process: Illicit Process of the Major Term and Illicit Process of the Minor Term.
INCONSISTENCY: e.g., Consider it reasonable for the Universe to continue to exist forever into the future, but judge absurd the possibility that it has infinite duration into the past.
INTERROGATION: The question asked has a presuppostion which the answerer may wish to deny, but which he/she would be accepting if he/she gave anything that would count as an answer. Any answer to the question "Why does such-and-such happen?" presupposes that such-and-such does indeed happen.
MEANINGLESS QUESTION: (e.g., What happens when an irresistible force meets an immovable object? But if there is such a thing as an irresistible force, there can be no immovable objects, and vice versa);
MISUNDERSTANDING STATISTICS: e.g., President Dwight Eisenhower expressing astonishment and alarm on discovering that fully half of all Americans have below average intelligence.
NON CAUSA PRO CAUSA: An argument to reject a proposition because of the falsity of some other proposition that seems to be a consequence of the first, but really is not.
NON-SEQUITUR: An argument in which the conclusion is not a necessary consequence of the premises. Another way of putting this is: A conclusion drawn from premises that provide no logical connection to it.
OBSERVATIONAL SELECTION: Also called the enumeration of favorable circumstances, or as the philosopher Francis Bacon described it, 'counting the hits and forgetting the misses" (e.g., A state boasts of the Presidents it has produced, but is silent on its serial killers);
Onus Probandi: Also called "The burden of proof". This is not a fallacy in itself, but rather is a general rule of proof - the person making the assertion carries the burden. The person defending against an assertion is not required to prove a negative (and it is questionable whether proving a negative is possible given the rules of logic and the contingency of inductive method). See "Shifting the burden of proof".
PETITIO PRINCIPII: See "Begging the Question".
POST HOC, ERGO PROPTER HOC: An argument from a premise of the form "A preceded B" to a conclusion of the form "A caused B." Simply because one event precedes another event in time does not mean that the first event is the cause of the second event. This argument resembles a fallacy known as a Hasty Generalization.
PLURIUM INTERROGATIONUM-MANY QUESTIONS: A demand for a simple answer to a complex question.
QUATERNIO TERMINORUM: An argument of the syllogistic form in which there occur four or more terms. In a standard categorical syllogism there are only three terms: a subject, a predicate, and a middle term.
RED HERRING: A fallacy when irrelevant material is introduced to the issue being discussed, such that everyone's attention is diverted away from the points being made, and toward a different conclusion. It is not logically valid to divert a chain of reasoning with extraneous points.
REIFICATION: To reify something is to convert an abstract concept into a concrete thing. Reification is a Fallacy of Ambiguity. Reification is also sometimes known as a fallacy of "hypostatization".
SECUNDUM QUID: See HASTY GENERALIZATION
SHIFTING THE BURDEN OF PROOF: The burden of proof is always on the person making the assertion or proposition. Shifting the burden of proof, a special case of "argumentum ad ignorantium", is a fallacy of putting the burden of proof on the person who denies or questions the assertion being made. The source of the fallacy is the assumption that something is true unless proven otherwise. See Onus Probandi.
SHORT-TERM VS LONG-TERM: A subset of the excluded middle. (e.g., We can't afford programs to feed malnourished children and educate pre-school kids. We need to urgently deal with crime on the streets.)
SLIPPERY SLOPE: Related to the excluded middle. (e.g., If we allow abortion in the first weeks of pregnancy, it will be impossible to prevent the killing of a full-term infant. Or, conversely: If the state prohibits abortion even in the ninth month, it will soon be telling us what to do with our bodies around the time of conception);
SPECIAL PLEADING: Special pleading is a logical fallacy wherein a double standard is employed by the person making the assertion. Special pleading typically happens when one insists upon less strict treatment for the argument he/she is making than he or she would make when evaluating someone else's arguments.
STATISTICS OF SMALL NUMBERS: A close relative of 'Observational Selection'. Having an inadequate sample size.
STRAW MAN: It is a fallacy to misrepresent someone else's position for the purposes of more easily attacking it, then to knock down that misrepresented position, and then to conclude that the original position has been demolished. It is a fallacy because it fails to deal with the actual arguments that one has made.
SUPRESSED EVIDENCE, OR HALF-TRUTHS: (e.g., An amazingly accurate and widely quoted "prophecy" of the assassination attempt on President Reagan is shown on television; but was it recorded before or after the event?)
SWEEPING GENERALIZATION: Also known by the Latin term "DICTO SIMPLICITER", a Sweeping Generalization occurs when a general rule is applied to a particular situation in which the features of that particular situation render the rule inapplicable. A sweeping generalization is the opposite of a hasty generalization.
TWO WRONGS MAKE A RIGHT (TU QUOQUE): Two wrongs never add up to a right; you cannot right a wrong by applying yet another wrong. Such a fallacy is a misplaced appeal to consistency. It is a fallacy because it makes no attempt to deal with the subject under discussion.
UNDISTRIBUTED MIDDLE: A syllogistic argument in which the middle term of a categorical syllogism is not distributed in at least one of the premises.
WEASEL WORDS: (e.g., calling a war a 'police action,' 'armed incursion,' 'protective reaction strike,' 'pacification,' safeguarding american interests,' etc.)