More than any other people on earth, we Americans are free to say and write what we think. The press can air the secrets of government, the corporate boardroom, or the bedroom with little fear of punishment or penalty. This extraordinary freedom results not from America's culture of tolerance, but from fourteen words in the constitution: the free expression clauses of the First Amendment.

In Freedom for the Thought That We Hate, two-time Pulitzer Prize-winner Anthony Lewis describes how our free-speech rights were created in five distinct areas--political speech, artistic expression,...