PHIL 110 Lecture Notes - Lecture 1: Deductive Reasoning, Formal System

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

Document Summary

Let (cid:862)p(cid:863) sta(cid:374)d for (cid:862)dr. m(cid:272) is a professor(cid:863). Let (cid:862)q(cid:863) sta(cid:374)d for (cid:862)dr. m(cid:272) is hu(cid:373)a(cid:374)(cid:863: p or q. It is not the case that q: all arguments that have that same pattern are valid. Sound argument: a valid argument with true premises. Must the conclusion of a sound argument be true: the conclusion of a sound argument must be true. Can logic tell us that an argument is sound: no, it can tell us only about formal properties, not truth, exception: logic can tell which statements are logically true or false. Can logic tell us that an argument is unsound: only sometimes, not always, logic can tell when an argument is unsound only when it is invalid or contains a logically false statement. It cannot distinguish valid arguments with (non-logically) true premises from valid arguments with (non-logically) false premises.