A rational process is a moral process. You may make an error at any step of it, with nothing to protect you but your own severity, or you may try to cheat, to fake the evidence and evade the effort of the quest - but if devotion to the truth is the hallmark of morality, then there is no greater, nobler, more heroic form of devotion than the act of a man who assumes the responsibility of thinking.

Ideas cannot be fought except by means of better ideas. The battle consists, not of opposing, but of exposing; not of denouncing, but of disproving; not of evading, but of boldly proclaiming a full, consistent, and radical alternative.

Civilization does not have to perish. The brutes are winning only by default.

The conservatives see man as a body freely roaming the earth, building sand piles or factories - with an electronic computer inside his skull, controlled from Washington. The liberals see man as a soul freewheeling to the farthest reaches of the universe - but wearing chains from nose to toes when he crosses the street to buy a loaf of bread.

Live and act within the limit of your knowledge and keep expanding it to the limit of your life. Redeem your mind from the hockshops of authority. Accept the fact that you are not omniscient, but playing a zombie will not give you omniscience-that your mind is fallible, but becoming mindless will not make you infallible-that an error made on your own is safer than ten truths accepted on faith, because the first leaves you the means to correct it, but the second destroys your capacity to distinguish truth from error.

The greatest threat to mankind and civilization is the spread of the totalitarian philosophy. Its best ally is not the devotion of its followers but the confusion of its enemies. To fight it, we must understand it.

I say that man is entitled to his own happiness and that he must achieve it himself. But that he cannot demand that others give up their lives to make him happy.