The point at which we recognize this need is much higher in some men than in others. The totalitarian rulers think they do not need the freedom of an opposition: They exile, imprison, or shoot their opponents. We have concluded on the basis of practical experience, which goes back to Magna Carta and beyond, that we need the opposition. We pay the opposition salaries out of the public treasury.

In so far as the usual apology for freedom of speech ignores this experience, it becomes abstract and eccentric rather than concrete and human. The emphasis is generally put on the right to speak, as if all that mattered were that the doctor should be free to go out into the park and explain to the empty air why I have a stomachache. Surely that is a miserable caricature of the great civic right which men have bled and died for. What really matters is that the doctor should tell me what ails me, that I should listen to him; that if I do not like what he says I should be free to call in another doctor; and that then the first doctor should have to listen to the second doctor; and that out of all the speaking and listening, the give-and-take of opinions, the truth should be arrived at.

This is the creative principle of freedom of speech, not that it is a system for the tolerating of error, but that it is a system for finding the truth. It may not produce the truth, or the whole truth all the time, or often, or in some cases ever.