Like most young physicists, when I was a kid enraptured with physics, I thought, "Everything can be explained by the theory of the atom!" But as I've gotten older, and I look at the world, I think there's a lot of ways in which that kind of building up from the smallest building blocks doesn't actually account for the world. As I've gotten older, I've also become sensitive to the ways - to all that is not amenable to explanation. Things that, even if you had an explanation, what good would it be?