I tried to engage a couple of colleagues in a metaphysical discussion last week. Actually, it was more of a metabiological thought experiment:
"Stand still," I said, "and imagine that you have suddenly sprouted a tail like a monkey's."
My colleagues looked at me sceptically.
"No, go on, I'm being serious. Imagine you've got a monkey's tail. Now here's my question: would you instinctively know how to move it about? Do you think your brain would be capable of sending a message via your nervous system to your new limb to tell it to move? Go on, try it now: try to move your imaginary tail. Can you do it?"
The sceptical looks turned to blank ones.
"Well I can!" I said. "I instinctively know how to move my imaginary tail around. In fact, I'm doing it right now!"
My colleagues told me I was weird.
I think about this sort of thing a lot.