断奶在幼儿生命中是个重要的转折点，我们不该让孩子继续吸吮而不咀嚼食物。

The reality is: sometimes you lose. And you’re never too good to lose. You’re never too big to lose. You’re never too smart to lose. It happens.

The progress of mathematics is measured by the number of problems it can solve.

The first fruit of this imagination - and the first lesson of the social science that embodies it - is the idea that the individual can understand his own experience and gauge his own fate only by locating himself within his period, that he can know his own chances in life only by becoming aware of those of all individuals in his circumstances.