PP201 Chapter Notes - Chapter 4b: Deductive Reasoning, Peanut Butter
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Sufficient conditions, what follows i(cid:373)(cid:373)ediately after the word (cid:862)if (cid:863, (cid:862)all(cid:863) sig(cid:374)als a suffi(cid:272)ie(cid:374)t (cid:272)o(cid:374)ditio(cid:374, deductive arguments: if the premises are true, the conclusion must be true. If the sentence has only if: whe(cid:374) a se(cid:374)te(cid:374)(cid:272)e starts with (cid:862)if (cid:863) the se(cid:272)o(cid:374)d part of the se(cid:374)te(cid:374)(cid:272)e is (cid:374)e(cid:272)essary. If the se(cid:374)te(cid:374)(cid:272)e (cid:272)o(cid:374)tai(cid:374)s (cid:862)u(cid:374)less(cid:863) sta(cid:374)dardize it so that it starts with (cid:862)if (cid:863) Valid arguments: valid arguments: arguments that affirm a sufficient condition or deny a necessary condition. If the premises are true the conclusion must be true: validity is necessary, but not sufficient for accepting a deductive argument. Invalid arguments: arguments that deny a sufficient condition or affirm a necessary condition. If it"s (cid:374)ot rai(cid:374)i(cid:374)g i do(cid:374)"t (cid:374)eed (cid:373)y u(cid:373)(cid:271)rella. It"s (cid:374)ot rai(cid:374)i(cid:374)g so i do(cid:374)"t (cid:374)eed (cid:373)y u(cid:373)(cid:271)rella: sufficient it"s (cid:374)ot rai(cid:374)i(cid:374)g, necessary i do(cid:374)"t (cid:374)eed (cid:373)y u(cid:373)(cid:271)rella, valid because the second sentence affirms the sufficient condition.
