Posted: March 2nd, 2017

For each of the following arguments, it is possible to provide a formal proof

of validity by adding just three statements to the premises. Writing these out, carefully and accurately, will strengthen your command of the rules of inference, a needed preparation for the construction of proofs that are more extended and more complex.

1. (H ⊃ I) · (H ⊃ J)

2. H · (I V J)

Therefore, I V J

9.5 B1

For each of the following arguments, a formal proof of validity can be constructed without great difficulty, although some of the proofs may require a sequence of eight or nine lines (including premises) for their completion.

1. A ⊃ B

2. A v (C · D)

3. B · E

Therefore, C

9.6 argument 1

For each of the following one-step arguments, state the one rule of inference by which its conclusion follows from its premise.

(A ⊃ B) ⋅ (C ⊃ D)

Therefore, (A ⊃ B) ⋅ (∼D ⊃ ∼C)

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