[PeterStuer]

Same as below, You can prove that something can not exist, typically by proving its existence would lead to a contradiction. You can also prove exhaustively that some thing that can exist does in fact not exist if the set of potential evidence of existence is finite. where you run into trouble is in cases were something could exist, but the set of potential evidence is infinite or for practical purposes beyond the means of exhaustive coverage.

IMHO, not a professional philosopher