basic validity question: Philosophy Forums

basic validity question

Algazel
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Posted 10/23/09 - 06:59 AM: Subject: basic validity question	#1
Hi, i'm just looking through my week 3 propositional homework and i just want to clarify that i understand the question properly: I need to show if the following arguments are valid: 1. A and ¬ A, So B - I take it this valid because since the premise can never be true, in propositional logic any conclusion holds. and 2. A ? ¬A, so ¬A - this is also true because the premise is true when A is false; the conclusion is also true when A is false If someone could clarify that i'm understanding this correctly

Algazel
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Posted 10/23/09 - 07:06 AM:	#2
sorry, the '?' symbol came out for the material implication

Timothy
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Posted 10/23/09 - 08:38 AM:	#3
looks like you've got it... insofar as it's impossible to find a truth-table line where the premises are true and the conclusion false, such an argument will always be valid (which does not mean that it's a sound argument)
"Neither Aristotelian nor Russellian rules give the exact logic of any expression of ordinary language; for ordinary language has no exact logic." P.F. Strawson

Kelby
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Posted 10/23/09 - 12:08 PM:	#4
Algazel wrote: 1. A and ¬ A, So B - I take it this valid because since the premise can never be true, in propositional logic any conclusion holds. Yes this is valid. Keep in mind anything can be concluded from a contradiction. 2. A ? ¬A, so ¬A - this is also true because the premise is true when A is false; the conclusion is also true when A is false If someone could clarify that i'm understanding this correctly you are understanding it just fine. :-)

Algazel
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