PHIL 101 Lecture 28: Intro to Logic, Lecture 28
7 Dec 2016
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Com (commutation) p * q :: q * p p v q :: q v p. Assoc (association) p * (q * r) :: (p * q) * r p v (q v r) :: (pvq) v r. Dist (distribution) p * (q v r) :: (p * q) v (p * r) p v (q * r) :: (p v q) * (p v r) Taut (tautology) p :: (p * p) p :: (p v p) Inference must work top to bottom: must be main connective. Can start on either side and go either way: may be applied anywhere within a premise does not have to be main connective, most proofs will require at least one substantive use of inference rules. ~b v c: a / c, b 1,3, mp. ~~b 4, dn: c 2,5, ds. Ex: c v ~d / ~(~c * d)
