Quantum field theory, which was born just fifty years ago from the marriage of quantum mechanics with relativity, is a beautiful but not very robust child.

If (the antiproton) had not been discovered, the foundations of physics really would have crumbled.

It was one time when people thought the value of the fine structure constant was important. Now of course it's still important, of course, as a practical matter,but we now know that the value it has is a function, that in any fundamental theory you derive the fine structure constant as a function of all sorts of mass ratios and so on and it's not really that fundamental.

This is one of the great social functions of science - to free people from superstition

There is now a feeling that the pieces of physics are falling into place, not because of any single revolutionary idea or because of the efforts of any one physicist, but because of a flowering of many seeds of theory, most of them planted long ago.

I now want to tell three stories about advances in twentieth-century physics. A curious fact emerges in these tales: time and again physicists have been guided by their sense of beauty not only in developing new theories but even in judging the validity of physical theories once they are developed. Simplicity is part of what I mean by beauty, but it is a simplicity of ideas, not simplicity of a mechanical sort that can be measured by counting equations or symbols.

Sometimes nature seems more beautiful than strictly necessary.