Andrew M. Gleason Quote

Often enough mathematicians have been caught off base with some pathological wrinkle in some funny function or something so, you know, you do have to do the proof, but still in the end that much more important function of a proof in my view is to figure out why it works.

In: D. Albers, G. Alexanderson and C. Reid, More Mathematical People: Contemporary Conversations (p. 97)