A man may die, nations may rise and fall, but an idea lives on. Ideas have endurance without death.

The great enemy of truth is very often not the lie--deliberate, contrived and dishonest--but the myth--persistent, persuasive and unrealistic. Too often we hold fast to the cliches of our forebears. We subject all facts to a prefabricated set of interpretations. We enjoy the comfort of opinion without the discomfort of thought.

[Commencement Address at Yale University, June 11 1962]

The one unchangeable certainty is that nothing is unchangeable or certain.

Efforts and courage are not enough without purpose and direction.

There are risks and costs to a program of action, but they are far less than the long-range risks and costs of comfortable inaction.

Change is the law of life. And those who look only to the past or present are certain to miss the future.