What do you consider the greatest intellectual achievement of mankind?

In light of Alan Turing's 100th birthday, I'm looking for a list of the greatest ideas conceived in history: anything from philosophy, math, computation, music, physics, artificial intelligence, etc. What do you think are the highlights of human thought?

I personally think Goedel's incompleteness theorems are the cleverest ideas I've seen. It makes metamathematics feel exciting and beautiful. I wish this kind of stuff was taught along with calculus/trig in high school...