You have enemies? Good. That means you've stood up for something, sometime in your life.

The goal of education is not to increase the amount of knowledge but to create the possibilities for a child to invent and discover, to create men who are capable of doing new things.

The greatest threat to our planet is the belief that someone else will save it.

勇气是所有美德中最重要的，因为没有勇气，你就无法始终如一地实践其他美德。