INFS1603 Lecture Notes - Lecture 9: Modus Tollens, Modus Ponens, University Of New South Wales

• School: UNSW, UNSW Sydney
• Department: Information Systems
• Course: INFS1603
• Professor: All

Document Summary

Inference: the pro(cid:272)ess or the out(cid:272)o(cid:373)e of (cid:858)i(cid:374)ferri(cid:374)g(cid:859) (cid:894)(cid:858)deri(cid:448)i(cid:374)g (cid:271)y reaso(cid:374)i(cid:374)g(cid:859) or (cid:858)(cid:272)o(cid:374)(cid:272)ludi(cid:374)g fro(cid:373) pre(cid:373)ises or evidence: deductive inferences: arriving at conclusions based on the strict logical consequences of (assumed true) premises. Inductive inferences: arriving at some conclusion that, though it is not logically derivable from the assumed premises, possesses some degree of probability relative to the premises. In logic, modus ponens and modus tollens are two forms for making valid inferences/valid arguments. If p is true, the(cid:374) q is true (cid:894)da(cid:374)iel is relia(cid:271)le, so (cid:449)he(cid:374) it(cid:859)s le(cid:272)ture ti(cid:373)e, da(cid:374)iel is at unsw(cid:895: p is true (cid:894)it(cid:859)s le(cid:272)ture ti(cid:373)e(cid:895, therefore, q is true (therefore, daniel is at unsw) In logic, an argument is a set of statements. Some statements, the premises, are intended to support other statements, the conclusions. (cid:858)valid(cid:859) argu(cid:373)e(cid:374)t =/= (cid:858)true(cid:859) argu(cid:373)e(cid:374)ts. Valid means that the argument is following a logical structure. Valid does not mean that the contents are true.