rules for categorical syllogisms

undistributed middle

in valid categorical syllogisms, middle term must be distributed at least once

illicit major or minor

if a term is distributed in the conclusion, must be distributed in one of the premises

MAJOR: if major term not distributed

MINOR: if minor term not distributed

exclusive premise

in a categorical syllogism the premises can’t both be negative

drawing an affirmative conclusion from a negative premise or vice versa (DAN)

in a valid categorical syllogism, a negative premise requires a negative conclusion and a negative conclusion requires a negative premise

existential fallacy

in a valid categorical syllogism if the conclusion is particular the premises can’t both be universal

4 terms

in a valid categorical syllogism, there must be exactly 3 terms, each of which is used in the same sense throughout