Posted: May 17, 2012 5:48 pm
amkerman wrote:Listen. Premis 1 and premise 2 cannot both live in the same universe.
The argument:
All dogs are black
All dogs are not black
All dogs are not black
Is not valid.
Actually, it is. Look up the definition of valid:-
http://en.wikipedia.org/wiki/Validity
This argument is inconsistent. Since classical logic is explosive, any possible conclusion validly follows.
The argument is not sound, the argument is not consistent the argument is valid though. This is in contrast to your argument in the OP which is neither sound, nor valid, and of nebulous consistency.
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While I'm here I'd like to congratulate Shrunk for a series of excellent posts on p4-5 running up to this one. I thumbed them all up for being clear and correct. They point out a number of the direct errors Amkerman has made.