By telling me you are.
If you ask ChatGPT if it is sentient, or has any thoughts, or experiences any feelings, what is its response?
But suppose it’s lying.
We also understand the math underlying it. Humans designed and constructed it; we know exactly what it is capable of and what it does. And there is nothing inside it that is capable of thought or feeling or even rationality.
It is a word generation algorithm. Nothing more.