from Kevin Williamson at National Review, Put Down the Torch, Pick Up a Book:
One of the most important arguments for freedom of mind — the freedom that comprehends freedom of speech, freedom of the press, freedom of association, freedom of inquiry, freedom of religion, etc. — is that the thought police are very likely to be wrong about things. Whether they are acting in the context of a free society or an unfree one, people who wield political power tend to reflect very strongly the prejudices of their time, their nation, their race, their class, their sex, their religion, their political party, etc. And we do not have to speculate about how things work out when new ideas — or new facts — encounter a political force invested with the power to suppress them: We have many examples in the historical record. Galileo was right and the Inquisition was wrong, but the Inquisition had the power to prohibit Galileo’s books, which might never have seen the light of day if not for the efforts of the heroes who smuggled his manuscripts out of Italy so that they could be published in Amsterdam.
Free speech and freedom of mind, if we understand them properly, should be rooted in intellectual humility. It is possible — it is certain — that some of the things we believe are wrong, be those matters of fact, matters of moral judgment, or estimates of the dangers posed by words and ideas that offend us. Be honest with yourself: If you had been present at the trials of Galileo, and everything you knew or had ever known pointed to his being in the wrong — the evidence of your eyes and all common human experience, the views of the most learned men and trusted of your community, every book on the subject you’d ever heard of, the proclamations of both church and state — do you think you would have made the right call? And that was, in a sense, an easy question — a question of fact that could be answered with mathematics and observation.
If you think that you do not have it in you to hang a witch or to burn a heretic, you’re probably wrong about that, too.