Peace cannot be kept by force; it can only be achieved by understanding.

You do not really understand something unless you can explain it to your grandmother.

I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones.

Every kind of peaceful cooperation among men is primarily based on mutual trust and only secondarily on institutions such as courts of justice and police.

Any fool can know. The point is to understand.

We cannot solve our problems with the same thinking we used when we created them.