学习本质上是刺激-反应连接的问题。

——《中国同盟会革命方略》（1906年秋冬间）

The human being cannot live in a condition of emptiness for very long: if he is not growing toward something, he does not merely stagnate; the pent-up potentialities turn into morbidity and despair, and eventually into destructive activities.

The most important thing is to keep your mind active.