Existence by definition is to "have being or reality". Reality is the "state of things as they are". Therefore it doesn't matter if I or you exist or not, we are perceived and therefore exist as reality. Therefore I prove I am me because with your limited information of me, I being me is the most likely explanation presented and therefore what you perceive and accept as reality. Essentially, you can't prove I am not me and so by default I am me. "Humans accept the reality they are presented with", I being me is the only reality you are presented with and there in, the only one you can accept. ;)