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

2. 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

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

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

5. 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.