老脑筋就像老马；如果你想保持它们的工作状态，就必须锻炼它们。
Old minds are like old horses; you must exercise them if you wish to keep them in working order.
数学的本质在于它的自由。
一本书是一面镜子：如果一只猿猴看进去，一个使徒几乎不可能看出去。
The smart way to keep people passive and obedient is to strictly limit the spectrum of acceptable opinion, but allow very lively debate within that spectrum.
The truth is not always beautiful, nor beautiful words the truth.
比死亡更强大的是爱，而非理性。
