What good is the warmth of summer, without the cold of winter to give it sweetness.

Take long walks in stormy weather or through deep snows in the fields and woods, if you would keep your spirits up. Deal with brute nature. Be cold and hungry and weary.

永远不要停止学习；一旦停止，你就会开始落后。

Consciousness serves the organism's need to interact effectively with its world.

The motor of our ingenuity is the question ‘Does it have to be like this?’, from which arise political reforms, scientific developments, improved relationships, better books.