Mathematics is not about numbers, equations, computations, or algorithms: it is about understanding.
数学不是关于数字、方程、计算或算法：它是关于理解的。
Memory is a fragile thing, easily distorted by time and politics.
No wise pilot, no matter how great his talent and experience, fails to use his checklist..
The theory of probabilities is at bottom nothing but common sense reduced to calculus.