"I think we've had to learn better the idea that the world is governed by a unified set of laws — which we don't yet know. ... physics and chemistry are not separate sciences. And even biology, as strongly influenced as it is by historical accidents — like the shapes of the continents and the fact that a comet may have hit the Earth sixty-five million years ago — biology itself doesn't have independent laws. There is no biological law that says organisms have to evolve to get better. That's a consequence of natural selection acting on heritable variations. ... The unity of science is something we've learned. I guess you could say we have unlearned the idea that there are separate, independent principles of physics, of chemistry, of biology — all standing at the same level of being equally fundamental."