I'm looking for quotations about how very simple mathematical ideas can be very powerful. I know of a few, but they're not quite what I'm looking for insofar as they contain criticism of other mathematicians, and I'm looking for quotations that are more unambiguously affirmative.

Two that are in the direction of what I'm looking for are:

1. The very notion of a scheme has a child-like simplicity - so simple, so humble in fact that no one before me had the audacity to take it seriously. So ”infantile” in fact, that for many years afterwards, and in spite of all the evidence, for so many of my ”learned” colleagues, it was treated as a triviality. – Alexander Grothendieck

2. It is the snobbishness of the young to suppose that a theorem is trivial because the proof is trivial. – John Whitehead

Any better examples?