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

I do not see how a man can work on the frontiers of physics and write poetry at the same time. They are in opposition.

Hopes are always accompanied by fears, and, in scientific research, the fears are liable to become dominant.

Mathematics is the tool specially suited for dealing with abstract concepts of any kind and there is no limit to its power in this field.

It is more important to have beauty in one's equations than to have them fit experiment... It seems that if one is working from the point of view of getting beauty in one's equations, and if one has really a sound insight, one is on a sure line of progress. If there is not complete agreement between the results of one's work and experiment, one should not allow oneself to be too discouraged, because the discrepancy may well be due to minor features that are not properly taken into account and that will get cleared up with further developments of the theory.

It seems that if one is working from the point of view of getting beauty in one's equations, and if one has really a sound insight, one is on a sure line of progress.

I found the best ideas usually came, not when one was actively striving for them, but when one was in a more relaxed state… I used to take long solitary walks on Sundays, during which I tended to review the current situation in a leisurely way. Such occasions often proved fruitful, even though (or perhaps, because) the primary purpose of the walk was relaxation and not research.