"Well, to some extent I can. The idea of a sense datum is useful; I think of it as the thing that happens in our sensing system when we perceive something. Exactly how that ties in with a physical object is a philosophical question I can't say very much about. But I make a habit of thinking things through starting from whatever hard facts I can find that have to do with what I'm chewing on, and I've always thought that there's a key to this perception thing in the pains that people get from an amputated arm or leg. Have you heard about that?"
"You mean they can feel pain in an arm that's been cut off?"
"That's right. And that should be impossible, if pains are really where we think they are. Say you hit your thumb with a hammer, or you stub your toe. Where is the pain?"
"The pain has to be in the thumb, or in the toe. It can't be any other way. I know. It hurts like hell, right where you hit it! How can there be any question?"
"It sure seems that way. But no matter how much it hurts, or how strongly convinced we are that the thumb or toe is having pain, that's not what happens.
The pain… is in… the brain."
"Mr. Sean, that's really hard to imagine. When you hurt yourself the feeling of pain is so immediate, so sharply localized. How can it really be in the brain? Especially considering that when surgery is done on the brain it needs no anesthetic. Because cutting into the brain does not give rise to pain!"