PHIL 10 Chapter 4: Replacement Rules, Indirect Proof, and Tautologies
Document Summary
Phil 10 textbook notes chapter 4: replacement rules, indirect proof, and. Inference rules go from one or more statements to one new statement that is implied by them: embody implications. Replacement rules go from one statement to one equivalent statement: embody equivalences, anything that is equivalent is an implication as well. Inference rules can be used in the same way as replacement rules, and vice versa. Conditional exchange (ce) (x y) :: (~x v y) (x v y) :: (~x y) Can apply replacement rules to parts of lines: rest of the line stays intact. Commutation (comm) (x v y) :: (y v x) (x y) :: (y x) 4. 4 last three replacement rules: dem, contra, assoc. Contraposition (cont) (x v y) v z :: x v (y v z) (x y) z :: x (y z) A ~(b v ~c: a (~b c, a (c ~b, (a c) ~b, a c, ~(~a v ~c, ~(a ~c, ~(c ~a)
