Subalternation

Subalternation is an <a href="/facts/Immediate_inference/yq5L6lQz">immediate inference</a> which is only made between A (All S are P) and I (Some S are P) <a href="/facts/Categorical_proposition/FGIFany3">categorical propositions</a> and between E (No S are P or originally, No S is P) and O (Some S are not P or originally, Not every S is P) categorical propositions of the traditional <a href="/facts/Square_of_opposition/z9S71UVr">square of opposition</a> and the original square of opposition. If the A proposition is true we may immediately infer that I is true. If the E proposition is true we may immediately infer that O is true. <a href="/facts/Converse_(logic)/VhlUrxxx">Conversely</a>, If the I is false, we can immediately infer that A is also false, as well as if O is false, then E is false. However, if the A proposition is false that will not tell us anything about the truth value of the I proposition. Similarly, if the E proposition is false, that will not tell us anything about the truth value of the O proposition.
An example of a subalternation is "If all leopards are mammals, then some leopards are mammals."
When the inference is misapplied, the <a href="/facts/Syllogistic_fallacy/nR2QwWot">syllogistic fallacy</a> is called an <a href="/facts/Illicit_subalternation/yq5L6lQz">illicit subalternation</a>.

Subalternation open-in-new

Subalternation