# Formal fallacies

Formal fallacies are fallacies which occur in arguments in formal logic, as well as in ordinary language. A formal fallacy occurs when it produces a contradiction within the system of premises. When a system of premises produces a contradiction, the entire system must be rejected, on the basis that a system containing a contradiction will prove the truth of any proposition, including the negation of the propositions granted by the system.

## List of Formal Fallacies

### Propositional Logic

Affirming a disjunct is a form of logical fallacy where an alternative possibility is rejected because the first is accepted, even if both are accurate.

Affirming the consequent is a type of logical fallacy where a premise is asserted as true simply because a conclusion implied by the premise is true.

Argument from fallacy is an argument that has one or more fundamentally wrong statements or points.

False dilemma occurs when one provides only two (or a few) answers to a question, giving the illusion that these choices exhaust all possibilities, when in fact they don't.

### Quantificational Logic

Existential fallacy is a type of logical fallacy when the existence of a thing is implied, when it otherwise shouldn't from the premises.

Illicit conversion is caused by the inversion of the subject and predicate in a proposition.

Proof by example is caused when an instantiation is claimed as evidence for a universal claim.

Quantifier shift occurs when the quantifiers of a statement are improperly transposed.

### Syllogistic Logic

Affirmative conclusion from a negative premise is when a categorical syllogism derives a positive conclusion from a negative premise.

Exclusive premises occurs when both of the premises in a syllogism are negative.

Four-term fallacy occurs when a categorical syllogism has more than three terms. Categorical syllogisms should only have three terms.

Illicit Major occurs when the major term is not distributed in the premises.

Illicit Minor occurs when the minor term is not distributed in the premises.

Undistributed middle occurs when the middle term is not distributed in the premises.

 v · d Logical fallacies
 v · d Formal fallacies
 Propositional logic Affirming a disjunct · Affirming the consequent · Argument from fallacy · False dilemma · Denying the antecedent Quantificational logic Existential fallacy · Illicit conversion · Proof by example · Quantifier shift Syllogistic Affirmative conclusion from a negative premise · Exclusive premises · Necessity · Four-term fallacy · Illicit major · Illicit minor · Undistributed middle

 v · d Faulty generalisations
 General Begging the question · Gambler's fallacy · Slippery slope · Equivocation · argumentum verbosium Distribution fallacies Fallacy of composition · Fallacy of division Data mining Cherry picking · Accident fallacy · Spotlight fallacy · Hasty generalization · Special pleading Causation fallacies Post hoc ergo propter hoc · Retrospective determinism · Suppressed correlative · Wrong direction Ontological fallacies Fallacy of reification · Pathetic fallacy · Loki's Wager
 v · d False relevance
 Appeals Appeal to authority · Appeal to consequences · Appeal to emotion · Appeal to motive · Appeal to novelty · Appeal to tradition · Appeal to pity · Appeal to popularity · Appeal to poverty · Appeal to spite · Appeal to wealth · Sentimental fallacy · Argumentum ad baculum Ad hominem Ad hominem abusive · Reductio ad Hitlerum · Judgmental language · Straw man · Tu quoque · Poisoning the well Genetic Fallacies Genetic fallacy · Association fallacy · Appeal to tradition · Texas sharpshooter fallacy