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.

I'm offended by the kind of smarmy religiosity that's all around us, perhaps more in America than in Europe, and not really that harmful because it's not really that intense or even that serious, but just... you know after a while you get tired of hearing clergymen giving the invocation at various public celebrations and you feel, haven't we outgrown all this? Do we have to listen to this?

Alas, Islam turned against science in the twelfth century. The most influential figure was the philosopher Abu Hamid al-Ghazzali, who argued in The Incoherence of the Philosophers against the very idea of laws of nature, on the ground that any such laws would put God's hands in chains. According to al-Ghazzali, a piece of cotton placed in a flame does not darken and smoulder because of the heat, but because God wants it to darken and smoulder. After al-Ghazzali, there was no more science worth mentioning in Islamic countries.

I enjoy being at a meeting that doesn't start with an invocation!

Our job in physics is to see things simply, to understand a great many complicated phenomena in a unified way, in terms of a few simple principles.

It does not help that some politicians and journalists assume the public is interested only in those aspects of science that promise immediate practical applications to technology or medicine.

Our mistake is not that we take our theories too seriously, but that we do not take them seriously enough.