chapter 6 - Logic and Reasoning PHIL 102 [10] 3 Oct 2011...

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Unformatted text preview: Logic and Reasoning PHIL 102 [10] 3 Oct 2011 Today: CHAPTER 6 Deductive Reasoning: Propositional Logic So far Arguments = a few sentences put together in order to support a conclusion Sentences = statements = claims = say that something is (or isnt) the case = can be true or false = have truth-value So far Arguments = a few sentences put together in order to support a conclusion Arguments: good or bad Good = valid + sound Bad = fallacies (various) So far Arguments = a few sentences put together in order to support a conclusion Arguments: good or bad Good = valid + sound Validity b the conclusion follows from the premises Propositional logic (= truth-functional logic) studies the logical relations between propositions / statements. Simple statements: John sleeps, John smokes Composite statements: John visited his mother and went shopping Propositional logic (= truth-functional logic) studies the logical relations between propositions / statements. Simple statements: John sleeps, John smokes Composite statements: John visited his mother and went shopping One thought / claim More than one thought / claim Propositional logic (= truth-functional logic) studies the logical relations between propositions / statements . Simple statements: John sleeps, John smokes Composite statements: John visited his mother and went shopping Relations of logical, not causal nature Relevant later! Method? b Symbolization 1. Identify simple statements 2. Assign a letters to them If Carter is the president , then the moon is made of green cheese . The moon is not made of green cheese . Therefore Carter is the not the president . Method? b Symbolization 1. Identify simple statements 2. Assign a letters to them If Carter is the president , then the moon is made of green cheese . The moon is not made of green cheese . Therefore Carter is not the president . P = Carter is the president Q = The moon is made of green cheese Method? b Symbolization 1. Identify simple statements 2. Assign a letters to them If Carter is the president , then the moon is made of green cheese . The moon is not made of green cheese . Therefore Carter is not the president . P = Carter is the president Q = The moon is made of green cheese P Not P Q Not Q Method? b Symbolization 1. Identify simple statements 2. Assign a letters to them If Carter is the president , then the moon is made of green cheese . The moon is not made of green cheese . Therefore Carter is not the president . P = Carter is the president Q = The moon is made of green cheese P Not P Q Not Q If P, then Q. Not Q. Therefore, not P. Method? b Symbolization 1. Identify simple statements 2. Assign a letters to them If Carter is the president , then the moon is made of green cheese . The moon is not made of green cheese . Therefore Carter is not the president ....
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chapter 6 - Logic and Reasoning PHIL 102 [10] 3 Oct 2011...

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