Phil12_S11_Valid_arguments(4-5-2011)

Phil12_S11_Valid_arguments(4-5-2011) - Valid Arguments Phil...

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Valid Arguments Phil 12: Logic and Decision Making Spring 2011 UC San Diego 4/5/2011 1 Tuesday, April 5, 2011
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Why cover statements and arguments Decision making (whether in science or elsewhere) involves reasoning based on evidence Question: when does some piece of information count as (good) evidence for or against a conclusion? - When does some piece of information (evidence) serve to support ( confrm ) or count against ( disconfrm ) a hypothesis or theory? To answer these questions we will cover arguments, and the statements of which they’re composed 2 Tuesday, April 5, 2011
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Review Statements are sentences that have a truth value —are either true or false - Contingent statements: could be true or could be false - Contradictions : always false - Tautologies : always true 3 Tuesday, April 5, 2011
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Review Criteria for evaluating arguments: - are the premises true? - is the argument valid? 4 Tuesday, April 5, 2011
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Validity An argument is valid iff it meets the following condition: if the premises were true, the conclusion must also be true - A valid argument cannot have true premises and a false conclusion This relationship is modal: it tells us what would be the case were certain conditions to be met - These conditions might not be satisFed in reality - The deFnition tells you nothing about what happens when they are not satisFed A way to test for validity: if you can imagine a situation in which the premises are true and the conclusion false, then the argument is not valid 5 Tuesday, April 5, 2011
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Validity 1. If I have a Ph.D., then I make a lot of money. 2. I have a Ph.D. 3. I make a lot of money. 6 Even though premise (1) is false, this argument is valid. Tuesday, April 5, 2011
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Validity 1. UCSD has a Cognitive Science department. 2. UCSD is located in California.
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Phil12_S11_Valid_arguments(4-5-2011) - Valid Arguments Phil...

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