PHIL 110 Lecture Notes - Lecture 17: Construals

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

Document Summary

Prove invalid: ( x)(px qx, ( x)(qx rx) / ( x)(px rx) Using the domain {a, b}, expand the following: ( x)[(ax bx) v cx] [(aa ba) v ca] v [(ab bb) v cb] (x)[(ax bx) v cx] To prove invalidity, expand each line: ( x)(ax bx, ( x)(bx cx, (aa ba) v (ab bb, (ba ca) v (bb cb) / (aa ca) v (ab cb) Prove invalid with model construction: (x)(fx gx) (x)(fx hx) The expansions of the two sentences: (x) [(fa ga) (x)(fb gb)] [(x)(fa ha) (x)(fb hb)] / [(fa ga) (x)(fa ha)] [(x)(fb gb) (x)(fb hb)] Hx = x is odd: the existence of an even number makes the conclusion false and the existence of an odd number makes the premise true at the same time. We can show the argument is invalid by making a furry, not gruesome, and hilarious, and making b furry, gruesome, and not hilarious. (cid:862)e(cid:454)te(cid:374)sio(cid:374)al(cid:863) (cid:448)s (cid:862)i(cid:374)te(cid:374)sio(cid:374)al(cid:863) (cid:272)o(cid:374)struals of predi(cid:272)ates.