Where?!
On what ham just said:
Well, then how do you know what YOU'RE sensing is from an outside stimulus?
Right now, I'm sitting here in a school library typing on a black Dell keyboard looking at these forums, watching the letters come up on the screen as I hit the keys. How do I know my hands are even moving at all? I could just be 'thinking' my hands are moving. Either that, or watching 'The Matrix' 300 billion times has melted everyones' brains into jello.