PHIL 110 Lecture Notes - Lecture 7: Truth Table, Logical Form, Modus Ponens

• School: Simon Fraser University
• Department: Philosophy
• Course: PHIL 110
• Professor: Jill Mc Intosh

Document Summary

Short truth table test of invalidity: avoids having to do the whole truth table, work in reverse. Assign t to all the premises and f to all the premises and f to the conclusion, and see if you can assign truth values to the atomic components in keeping with that. If you cannot, the argument is valid: problem: it can be difficult to tell whether you really cannot, or just did not, full truth tables are better for establishing validity. T f: q w, ~p ~w, w (p v q, r (s v t, s (q v n, / r (~q w) Find an interpretation in which they are all true: b a, c b, ~ c a / a c. B a, c b, ~c a, ~ (a c) If the premises are consistent, we can check the counterexample set for consistency. If it is consistent, the argument is invalid.