No new reading for Monday. Exam #2 is Wednesday. My office hours on Monday are cancelled. I’ll be out of town.

Exam #2: Outline -Use a truth-table to categorize a single statement (as a tautology, contradiction, or contingent statement) -Truth-table test for validity (method of exhaustive search) -Constructing an interpretation to test for validity -Proof of a theorem -Proof of an argument

~Elimination a1,…,an (j) ~q . b1,…,bn (k) q a1,…,an, b1,…,bn (m) ∧ j, k ~E j > k or j < k

~Introduction j (j) p Assumption . a1,…,an (k) ∧ {a1,…,an}/j (m) ~ p j, k ~I j > k, j < k, or j = k

DN (Double Negation) a1,…,an (j) ~~p . a1,…,an (k) p j, DN This rule is needed when you use ~I to derive something “positive” (i.e., something that does not have a tilde as its main connective). Assume the negation of your goal. Use ~I to get two adjacent tildes. Then use DN to arrive at your target.