Really? Which one? I mean, which one begins by saying, "there is not mathematical truth"?
and you believe the way to prove the existence of a thing is to deny its existence, say, God, for instance.
You are a treat.
Hank
Just curious: have you ever taken an upper level undergraduate math class -- something involving math analysis or complex variables?
As it happens, the technique is quite common, and easy (in the abstract) to understand. Suppose we want to prove A. If we assume ~A, and can then demonstrate that ~A leads to a contradiction, then A must be true.
Is it a universally applicable approach? I don't think so. But it does have its uses.