Hal Abelson on abstraction an design (from SICP videos)
PROFESSOR: Well, that's someone's axiom, and I bet that's the axiom of someone who hasn't implemented very large computer systems very much.
I said that computer science is a lot like magic and it's sort of good that it's like magic. There's a bad part of computer science that's a lot like religion. And in general, I think people who really believe that you design everything before you implement it basically are people who haven't designed very many things.
The real power is that you can pretend that you've made the decision and then later on figure out which one is right, which decision you ought to have made. And when you can do that, you have the best of both worlds.
Structure and Interpretation of Computer Programs » Video Lectures » 2B: Compound Data, around minute 00:37