This question always reminded me of the (excellent) book "Zen and the Art of Motorcycle Maintenance". The author explores the philosophy of engineering as being the art of separating things in to their components. At the risk of spoiling some of the book, a major struggle the author goes through is the paradox that there seems to be an infinite number of ways to split some kinds of systems, with no productive work ever being done. This question feels like that... you can split it down to the tiniest discrete system and you'll find you haven't gained much.

That's not to say that you wouldn't gain SOMETHING, nor that it's a bad interview question. I actually like it. It's just not terribly productive, in an engineering sense.