CPSC 121 Lecture Notes - Lecture 3: Soundness, Relevance Logic, If And Only If

• School: UBC
• Department: Computer Science
• Course: CPSC 121
• Professor: George Tsiknis

Document Summary

Logic is about valid inference, whether one sentence must be true given the truth of certain other sentences. If tim studies at ubc, he"ll get a good job. The conclusion must be true if the premises are true. If the argument is valid and all the premises are true, then the argument is both valid and sound. Validity: the conclusion follows, though the premises may be false. Sound: the conclusion follows, and all the premises are true. Because (b) has no premises, we can"t even ask if it"s a valid argument (a) is a question of validity (b) is a question of entailment (not very important) Validity: an argument is valid iff it is not possible for all the premises to be true and the conclusion false. An argument is valid if the conclusion is logically true (cannot be false), no matter what the premises are; a logically true statement follows from anything.