PHIL 120 Lecture 1: Module 5 Discussion Activity Answer Key
12 Mar 2016
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Module #5: group discussion activity answer key: for each of the following propositional form, decide whether the propositions under it are uniform substitution instances of that form. If yes, choose y, if not, choose n: p ~q, a ~a. Proof: make the following substitution: p a, q a. I. e. , if you replace (substitute) each occurrence of the symbol p in the original formula by. A , and each occurrence of the symbol q in the original formula by. A (and leave everything else unchanged (including all the other symbols and their order! )), you"ll get the desired formula which is a substitution instance of the original formula: ~a ~b. Proof: make the following substitution: p ~a, q b: ~a (b & c) Proof: no matter what substitution you make for q, you won"t be able to get rid of the negation sign before the original q. Note that the following substitution will not do: p ~a, q ~(b & c).
