Proof:
Rules of Inference Using Dilemmas

In a constructive dilemma, the first premise asserts a pair of conditional statements; the second premise says that at least one of the two antecedents is true; and the conclusion states that at least one of the two consequents is true.

A destructive dilemma argues that one of the two consequents is false and, therefore, that one of the two antecedents is false.

Constructive dilemma (CD)
Destructive dilemma (DD)
(p q)(r s)
(p q)(r s)
p v r
~ q v s
___
q v s
___
~ p v ~r


Disjunction and conjunction |
Hypothetical and disjunctive syllogisms | Dilemmas
Constructing a Proof

Proof

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