Mistake 1: “But” always introduces a negation. In fact, it may introduce an affirmative exceptive premise.
Mistake 2: Affirming the consequent of any connected conditional establishes its antecedent. Not unless the converse relation is separately known.
Mistake 3: Denying one side of every disjunction establishes the other. This fails in an exclusion-of-conjunction case.
Mistake 4: Every “or” statement has exactly one true side. In an exclusion-of-emptiness case, both sides may be true.
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Exceptive Syllogism: Valid Inferences from Connected and Disjunctive Conditionals
Mistake 1: “But” always introduces a negation. In fact, it may introduce an affirmative exceptive premise.
Mistake 2: Affirming the consequent of any connected conditional establishes its antecedent. Not unless the converse relation is separately known.
Mistake 3: Denying one side of every disjunction establishes the other. This fails in an exclusion-of-conjunction case.
Mistake 4: Every “or” statement has exactly one true side. In an exclusion-of-emptiness case, both sides may be true.