It is our misfortune that Anthony Lewis stopped writing his column for The New York Times in 2001. For more than thirty years, that column was the first place to look for commentary about public affairs that was informed by a deep knowledge of and commitment to constitutional rights, expressed clearly, gracefully, and forcefully. Lewis’s retirement deprived us of his voice just at the moment when Dick Cheney, David Addington, John Yoo, John Ashcroft, Viet Dinh, Alberto Gonzales, John Roberts, and all the other president’s men began rewriting the rules on wiretapping, prolonged detention without trial, habeas corpus, torture, military commissions, secret evidence, and, above all, the claimed authority of President Bush, as commander in chief, to exercise sole and unlimited power on matters involving national security. Though the post-9/11 assault on civil liberty is only touched upon glancingly in Freedom for the Thought That We Hate, Lewis’s short book is nevertheless a reminder of what we have been missing.

In the United States, as Lewis’s tales of the First Amendment confirm, the power vested in the courts to interpret the Constitution helped us to resist tyranny. And the area where we have fared best is this book’s subject: the First Amendment right to speak and publish. In that crucial respect, the present era differs markedly from previous periods when rights were under attack. From the time of the Sedition Act of 1798, to the period during and right after World War I when there were thousands of state and federal prosecutions for speech, to the post-World War II red scare, and again during the Nixon years when political surveillance reached a high point, the hallmark of repression was the effort to curb dissent. Not so today. The protections forged in the court cases discussed by Lewis in this book have by now gained such widespread acceptance that they are not seriously threatened by the “war on terror.” All of us continue to be free to speak out against abuses by our government.

Lewis derives the title of his book from one of the legendary dissents by Supreme Court Justice Oliver Wendell Holmes Jr. The case was United States v. Schwimmer, decided by the high court in 1929. A middle-aged pacifist immigrant from Hungary, Rosika Schwimmer, was denied citizenship because she refused to swear that she would take up arms to defend the United States. Holmes, who had been a Union soldier in the Civil War (he was eighty-eight when he dissented in Schwimmer) and wounded three times, had little use for pacifist opinions. Yet he wrote, in words that remain stirring despite their familiarity, that “if there is any principle of the Constitution that more imperatively calls for attachment than any other, it is the principle of free thought—not free thought for those who agree with us but freedom for the thought that we hate.”

As Lewis tells us, Holmes was not always a champion of free speech. Before making a radical shift in the turbulent year that followed World War I, Holmes took a constrained view of the First Amendment. Probably the lowest point was his opinion for the Supreme Court in early 1919 upholding the ten-year prison sentence imposed on Socialist leader Eugene V. Debs for violating the Espionage Act. Debs’s crime had been praising three men who had been imprisoned for failing to register for the draft. He said they “were paying the penalty for standing erect and for seeking to pave the way to better conditions for all mankind” and that he was “proud of them.” Later in the same year, however, Holmes dissented in another case involving prosecutions for opposing the war effort, this one carrying twenty-year prison sentences. Though his opinions thereafter in free-speech cases were almost always written in dissents, in which Justice Louis D. Brandeis regularly joined him, it is Holmes’s passion and poetry that has had a lasting influence. Today, it is hard to think about the First Amendment without calling to mind the soaring language of Holmes’s dissents of the 1920s.

Aryeh Neier , a former executive director of Human Rights Watch, is president of the Open Society Institute.