Date: Sat, 29 May 1999 19:38:40 -0400
Sender: Rod
Subject: invalid arguments

Level: 12th grade

Can an invalid argument have a true conclusion? If yes then why?


In the sense of formal logic - an 'argument': premises and conclusions (nothing else is looked at) is invalid only if the premises can (in some situation) be true and the conclusion be false (in the same situation).
    The essense of an argument is whether the premises and the conclusion are connected: The situations in which the premises are true are also situations which guarantee that the conclusion is true.
    Of course, the STEPS in between a set of true premises and a true conclusion may themselves contain a particular invalid argument: so that one would say that a 'proof' is invalid, even though the premises and the conclusion are true, if there is an intermediate step which is false when the preceeding step is true.
    In this sense a proof is a series of 'arguments', from one step to the next.


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