>Hate to be a killjoy, but a proof that negates its own proposition is itself invalid rather than just the proposition or conclusion.

And by the way, I don't think this is correct.

It is common in symbolic logic to assume a premise in order to find a contradiction. If you assume the opposite of what you want to prove, and it leads to a contradiction, then logically, what you assumed was false, and the opposite (conveinently what you wanted to prove) is true.

Or are we talking about two different things?