How can you not? It’s the case for every other animal out there (knock them unconscious and they no longer feel pain). How would one even have what it takes to feel anything without a brain? Reacting to a stimuli and understanding it is not the same.

Besides, by this same logic of “this can’t be proven”, it also can’t be proven plants don’t feel pain, since they also have the equivalent of nerves and response to stimuli.