Counterintuitive Facts (73): How Do You Prove People Around You Aren't Soulless NPCs?

I. Imagine such a being: He looks exactly like you on the outside. His brain neuron structure is exactly like yours. Every atom of his is identical to yours. If you pinch him, he screams. Because nerve signals transmit normally to his vocal cords. If you tell a joke, he laughs loudly. Because facial muscles contract normally. If you propose, he tears up and says yes. Because tear glands and speech center work normally. Physically and behaviorally, he's indistinguishable from you.

II. The only difference: he has no inner subjective experience. When you feel pain, you don't just have nerve signals. You have the "feeling of pain." That ache. That unbearableness. That desire for it to stop. But when he shows pain, it's just a mechanical reaction. Like a program outputting "Ouch!" But inside he