Quote:
Originally Posted by Renall
the cow isn't brown, then we know the negation is true that the cow is some color other than brown. The cow exists, and we can verify that statement, so we don't run into any problems. And even when speaking abstractly about things that exist, we know we at least could test them, so we know that either the proposition is true or its negation is true.
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But wait are you really sure about that?
To me this sounds the same as stating that if I say "Mark doesn't have a degree in astrophisics" then the statement "Mark has a degree in something other than astrophisics" is true.
I think that this example makes clear that there is fallacy here and that's the assumption that the negation of a specific quality of the degree the subject has implies that he still has a degree of a different quality. But we cannot deduce that by the original negation at all since the possibility that Mark has no degree at all exists.
The case of the cow you mentioned is tricky because you already know by
previous knowledge that a cow must have a color. However suppose you are an artificial intelligence with absolutely no knowledge of the concept of cows. Could you logically make that deduction? I think not.
At any rate if we do not possess the information of whether the cow exists or not then assuming that it must have a color is wrong. Which by extension means that in front of the sentence
the cow isn't brown we
cannot deduce that a cow that might or might not exist
must have a color other than brown.