[tkot]

Proof of my and your existence is impossible in a similar way - we could all be just brains in vats and all external stimuli might be hallucinations (or we could be just GPT-powered chat bots). In fact, I could be a hallucination of yours and you could be my hallucination. While the idea of solipsism is sort of an interesting thought experiment, it doesn't really help explain or predict anything.