### Post by Matheism on May 4, 2016 16:59:09 GMT 8

**Formal fallacies**

A formal fallacy is an error in logic that can be seen in the argument's form. All formal fallacies are specific types of non sequiturs.

**Anecdotal fallacy**– using a personal experience or an isolated example instead of sound reasoning or compelling evidence.

**Appeal to probability**– is a statement that takes something for granted because it would probably be the case (or might be the case).

**Argument from fallacy**– assumes that if an argument for some conclusion is fallacious, then the conclusion is false.

**Base rate fallacy**– making a probability judgment based on conditional probabilities, without taking into account the effect of prior probabilities.

**Conjunction fallacy**– assumption that an outcome simultaneously satisfying multiple conditions is more probable than an outcome satisfying a single one of them.

**Masked man fallacy (illicit substitution of identicals)**– the substitution of identical designators in a true statement can lead to a false one.

**Propositional fallacies**

A propositional fallacy is an error in logic that concerns compound propositions. For a compound proposition to be true, the truth values of its constituent parts must satisfy the relevant logical connectives that occur in it (most commonly: <and>, <or>, <not>, <only if>, <if and only if>). The following fallacies involve inferences whose correctness is not guaranteed by the behavior of those logical connectives, and hence, which are not logically guaranteed to yield true conclusions.

*Types of Propositional fallacies:*

**Affirming a disjunct**– concluded that one disjunct of a logical disjunction must be false because the other disjunct is true; A or B; A, therefore not B.

**Affirming the consequent**– the antecedent in an indicative conditional is claimed to be true because the consequent is true; if A, then B; B, therefore A.

**Denying the antecedent**– the consequent in an indicative conditional is claimed to be false because the antecedent is false; if A, then B; not A, therefore not B.

**Quantification fallacies**

A quantification fallacy is an error in logic where the quantifiers of the premises are in contradiction to the quantifier of the conclusion.

*Types of Quantification fallacies:*

**Existential fallacy**– an argument that has a universal premise and a particular conclusion.

**Formal syllogistic fallacies**

**Syllogistic fallacies**– logical fallacies that occur in syllogisms.

**Affirmative conclusion from a negative premise (illicit negative)**– when a categorical syllogism has a positive conclusion, but at least one negative premise.

**Fallacy of exclusive premises**– a categorical syllogism that is invalid because both of its premises are negative.

**Fallacy of four terms (quaternio terminorum)**– a categorical syllogism that has four terms.

**Illicit major**– a categorical syllogism that is invalid because its major term is not distributed in the major premise but distributed in the conclusion.

**Illicit minor**– a categorical syllogism that is invalid because its minor term is not distributed in the minor premise but distributed in the conclusion.

**Negative conclusion from affirmative premises (illicit affirmative)**– when a categorical syllogism has a negative conclusion but affirmative premises.

**Fallacy of the undistributed middle**– the middle term in a categorical syllogism is not distributed.