http://www.mathacademy.com/pr/quotes/index.asp?PHR=proof&ACTION=SEARCH

We are not very pleased when we are forced to accept a mathematical truth by virtue of a complicated chain of formal conclusions and computations, which we traverse blindly, link by link, feeling our way by touch. We want first an overview of the aim and of the road; we want to understand the idea of the proof, the deeper context.

– Hermann Weyl