Physics has a history of synthesizing many phenomena into a few theories.

Einstein's gravitational theory, which is said to be the greatest single achievement of theoretical physics, resulted in beautiful relations connecting gravitational phenomena with the geometry of space; this was an exciting idea.

Gravitation is, so far, not understandable in terms of other phenomena.

From the point of view of basic physics, the most interesting phenomena are, of course, in the new places, the places where the rules do not work - not the places where they do work! That is the way in which we discover new rules.

With the exception of gravitation and radioactivity, all of the phenomena known to physicists and chemists in 1911 have their ultimate explanation in the laws of quantum electrodynamics.

What I am going to tell you about is what we teach our physics students in the third or fourth year of graduate school... It is my task to convince you not to turn away because you don't understand it. You see my physics students don't understand it... That is because I don't understand it. Nobody does.