LessonsExceptive Syllogism: Valid Inferences from Connected and Disjunctive ConditionalsQuiz

Suppose we reason: “If this figure is a square, it has four sides.” We then establish that it is a square. Four-sidedness follows because of the true conditional.

But if the conditional is false — for example, “If something is a stone, it is alive” — asserting its antecedent does not make the consequent factually true.

Validity of an inference and truth of its premises are different questions. A valid exceptive form guarantees that a false conclusion cannot follow from premises that are all true.

Opening interactive controls...

The condition behind affirming the antecedent

Exceptive Syllogism: Valid Inferences from Connected and Disjunctive Conditionals

Suppose we reason: “If this figure is a square, it has four sides.” We then establish that it is a square. Four-sidedness follows because of the true conditional.

But if the conditional is false — for example, “If something is a stone, it is alive” — asserting its antecedent does not make the consequent factually true.

Validity of an inference and truth of its premises are different questions. A valid exceptive form guarantees that a false conclusion cannot follow from premises that are all true.