Given the argument: R ∨ I / ∼ S ∨ (R ⊃ I) // S ⊃ I This argument is: A) Valid. B) Invalid; fails in 4^th line. C) Invalid; fails in 2^nd line. D) Invalid; fails in 5^th line. E) Invalid; fails in 3^rd line.

Question

Quizplus · Accepted Answer

The argument is valid because if we assume S is true, then given S ⊃ I, I must be true. If S is false, then ∼S is true, and given ∼S ∨ (R ⊃ I), either R ⊃ I is true or it doesn't matter because ∼S is true. In either case, I can be concluded, making the argument valid.

Given the Argument: R ∨ I / ∼ S ∨