In my paper the fact the XY ...

In my paper the fact the XY was not equal to YX was very disagreeable to me. I felt this was the only point of difficulty in the whole scheme...and I was not able to solve it.
 Werner Heisenberg

Quotes from the same author

We will have to abandon the philosophy of Democritus and the concept of elementary particles. We should accept instead the concept of elementary symmetries.
 Werner Heisenberg
Nature is made in such a way as to be able to be understood. Or perhaps I should put it-more correctly-the other way around, and say that we are made in such a way as to be able to understand Nature.
 Werner Heisenberg
It will never be possible by pure reason to arrive at some absolute truth.
 Werner Heisenberg
In general, scientific progress calls for no more than the absorption and elaboration of new ideas- and this is a call most scientists are happy to heed.
 Werner Heisenberg
Science no longer is in the position of observer of nature, but rather recognizes itself as part of the interplay between man and nature. The scientific method ... changes and transforms its object: the procedure can no longer keep its distance from the object.
 Werner Heisenberg