I think it is the general rule that the originator of a new idea is not the most suitable person to develop it, because his fears of something going wrong are really too strong... At age 69.

The physicist, in his study of natural phenomena, has two methods of making progress: (1) the method of experiment and observation, and (2) the method of mathematical reasoning. The former is just the collection of selected data; the latter enables one to infer results about experiments that have not been performed. There is no logical reason why the second method should be possible at all, but one has found in practice that it does work and meets with reasonable success.

A great deal of my work is just playing with equations and seeing what they give.

It is more important to have beauty in one's equations than to have them fit experiment.

When [Erwin Schrödinger] went to the Solvay conferences in Brussels, he would walk from the station to the hotel where the delegates stayed, carrying all his luggage in a rucksack and looking so like a tramp that it needed a great deal of argument at the reception desk before he could claim a room.

The methods of theoretical physics should be applicable to all those branches of thought in which the essential features are expressible with numbers.

A theory with mathematical beauty is more likely to be correct than an ugly one that fits some experimental data.