Section 9.3

Section 9.3 - derision • 4. A v C 3, addition • 5. D 2,...

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Section 9.3 Review and questions about 9.2 homework #10 same as #20 Formal proof of validity 1. Sequence of Statements 2. Every statement either is a premise in the argument or follows from one or more previous statements by means of a rule of inference 3. Last statement in the sequence is the conclusion of the argument Consider the following argument: A•B, (A v C) D, therefore: A•D Start off with premises as first statements in proof 1. A•B 2. (A v C) D 3. A 1, simplification (line you got it from, justification for
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Unformatted text preview: derision • 4. A v C 3, addition • 5. D 2, 4, MP • 6. A•D 3,5, conj Formal proof demonstrates the validity of the above argument, can infer conclusion from premises Another Example: (E v F) • (G v H) (E G) • (F H) ~G therefore H 1. E v F • G v H trying to get H 2. (E G) • (F H) 3. ~G 4. E v F 1, simplification 5. E G 2, simp 6. ~E 3,5 MT 7. F 4, 6 Disjunctive Syllogism 8. G v H 2,4, CD 9. H 3,8, Disj. Syllogism...
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This note was uploaded on 03/16/2011 for the course PHIL 045 taught by Professor Hopper during the Fall '07 term at GWU.

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Section 9.3 - derision • 4. A v C 3, addition • 5. D 2,...

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