PHIL 110 Lecture Notes - Lecture 9: Modus Tollens, Modus Ponens, Disjunctive Syllogism
16 Mar 2017
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Dr mc"s philosophy 110 (1171) part notes 5#2 . From last time: instead, we"re going to learn some rules of inference. What logically follows from what, and what is logically equivalent to what. Do not confuse these valid patterns with their evil look-alikes. invalid form: example invalid form: Each line of a proof must either be a premise or follow validly from something that came before it: ~r, s r. Is this valid: p v q, p / ~q. Simplification (simp: p q / p. Also: p q / q. Conjunction (conj) p q / p q. Consider the following rule: p / p v q. Is this valid: p / p q. A proof of an argument is finite series of sentence forms such that each member of the series is either a premise or follows from a line or that came before, with the last line being the argument"s conclusion.
