# lect09 - INTRO LOGIC DAY 09 1 UNIT 2 DERIVATIONS IN...

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1 1 INTRO LOGIC DAY 09 2 UNIT 2 DERIVATIONS IN SENTENTIAL LOGIC

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2 3 Basic Idea We start with a few argument forms, which we presume are valid, and we use these to demonstrate that other argument forms are valid. We demonstrate that a given argument form is valid by deriving ( deducing ) its conclusion from its premises using a few fundamental modes of reasoning . 4 Example 1 – Modus Ponens (MP) –––––– we can employ modus ponens (MP) to derive the conclusion from the premises. if then –––––––––– P P Q Q R R S –––––– S a derivative argument form
3 5 Example 1 (continued) / S ; R S ; Q R ; P Q P MP Q R S 6 Example 2 – Modus Tollens (MT) we can employ modus tollens (MT) to derive the conclusion from the premises. a derivative argument form if then not –––––––––– not S R S Q R P Q –––––– P ––––––

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4 7 Example 2 (continued) / P ; P Q ; Q R ; R S
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## This note was uploaded on 02/04/2012 for the course PHIL 110 taught by Professor Bohn during the Fall '08 term at UMass (Amherst).

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lect09 - INTRO LOGIC DAY 09 1 UNIT 2 DERIVATIONS IN...

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