数学不是一门演绎科学——那是陈词滥调。当你试图证明一个定理时，你不仅仅是列出假设然后开始推理。你所做的是反复试验、实验和猜测。

"We are all haunted by the past, and the past is always present."

The purpose of abstraction is not to be vague, but to create a new semantic level in which one can be absolutely precise.

你知道得越多，就越意识到自己知道得多么少。