PHI 108 Chapter 8: Natural Deduction, Sections A-D
18 Jan 2019
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Document Summary
Natural deduction - a proof procedure by which the conclusion of an argument is validly derived from the premises through the use of rules of inference. Rules of inference - the function of rules of inference is to justify the steps of a proof. Proof - a sequence of steps (also called a deduction or a derivation) in which each step either is a premise or follows from earlier steps in the sequence according to the rules of inference. A justification of a step includes a rule of inference and the prior steps that were used to derive it. This procedure guarantees that each step follows validly from prior steps. A proof ends when the conclusion of the argument has been correctly derived. Implication rules - valid argument forms that are validly applied only to an entire line. Replacement rules - pairs of logically equivalent statements forms.
