ChatGPT: Can I irrefutably prove that someone else exists?
No, you cannot irrefutably prove that someone else exists—at least not in the strict philosophical sense of "irrefutable."
Here's why:
1. Epistemological Limitation
The only thing that can be irrefutably known, according to Descartes and much of modern epistemology, is your own conscious experience:
“Cogito, ergo sum” – I think, therefore I am.
All external perceptions—including other people—could, in principle, be:
hallucinations,
dreams,
a simulation (like in The Matrix),
or deceptions by an evil demon (Descartes’ thought experiment).
In any of those cases, the “others” you experience could be illusions, even if they feel real.
2. Solipsism Challenge
Solipsism is the idea that only your own mind is sure to exist. Everything else is uncertain. You cannot step outside your own mind to verify whether the beings you perceive are truly conscious entities with independent existence.
3. Empirical vs. Logical Proof
You may have empirical evidence (e.g. conversations, interactions, reactions), but these:
depend on your senses (which can be deceived),
and are not logically necessary truths.
So, while you can reasonably believe others exist (and live accordingly), you cannot logically deduce their existence in a way that is immune to doubt.
Summary

You can rationally believe others exist.

But you cannot irrefutably prove their existence, because all such claims depend on sensory input or assumptions that might not hold.