At the moment most of the amendments in the Bill of Rights seem particularly suited to one party and not the other. The Second Amendment, the right to bear arms, is very Republican. The Eighth Amendment, prohibiting cruel and unusual punishment, is very Democratic. The 10th Amendment, giving power to the states, was Republican until that party got full control of the federal government. Now it’s trending strongly Democratic.

The only completely nonaligned amendment is the First, which neither party has ever been able to claim, particularly the part mandating the freedom of speech. Democrats invoke it when defending musicians’ right to cuss and protesters’ right to criticize the war on terror. Republicans invoke it when defending the right to donate to political campaigns and to speak out on college campuses.

American courts give more credit to freedom of speech than the courts of any other country. The idea defines how we see ourselves – and the debasement that others see in us, too. In a way this is surprising. The Bill of Rights was an afterthought to the constitution – which is why they are called “amendments.” But, somehow, free speech both was, and became, fundamentally American. Two new books tell very different parts of that story.

The first is Floyd Abrams’s “Speaking Freely” (Viking, 336 pages, $25.95). A partner at Cahill, Gordon & Reindel, Mr. Abrams got his start defending the right of the New York Times to publish the Pentagon Papers. Now he’s a ubiquitous part of every high-profile American free speech conflict, from the Valerie Plame leak investigation to the Columbia anti-Semitism scandal.

Mr. Abrams splits his memoir into nine chapters, each detailing a case he has worked on. He writes marvelously, and each chapter contains the elements of a terrific short story: drama, suspense, and riveting characters. He defended NBC from charges that it libeled Wayne Newton, blistering the king of Las Vegas during cross-examination. He defended the Brooklyn Museum from Rudolph Giuliani’s wrath, when the mayor tried to evict it from its building after declaring an exhibit offensive. In an out-of-court settlement, the museum dropped its lawsuit charging the city with violating its freedom of expression in exchange for the city putting $5.8 million into redesigning the museum’s entrance.

Unfortunately, however, Mr. Abrams never explains where his philosophy comes from and where it ends. He blandly declares that “while there are always arguments available in support of suppressing speech, society is almost always better served when those arguments are rejected,” but goes no further. Late in the book, he criticizes liberals for abandoning free speech principles when it comes to campaign finance reform. But he stops well short of explaining how far his defense of free speech goes. Mr. Abrams’s failure to drill deeper suggests that he’s more a tactical than an intellectual master of the subject.

If Mr. Abrams’s account lacks history and explanation, he is more than compensated for by John Durham Peters. A professor at the University of Iowa, the author of “Courting the Abyss: Free Speech and the Liberal Tradition” (University Of Chicago Press, 316 pages, $29) wants to trace free speech from the Garden of Eden to present-day Nazi marches. His core idea is that the originators of free speech had a much more complex view of it than its strongest advocates – say Floyd Abrams – have today.

Mr. Peters wants a “hardhearted” defense of free speech, one which recognizes the benefits that can come by letting everyone have a say but doesn’t rely on “prissy” platitudes. For example, he cites the old saying attributed (falsely, he shows) to Voltaire that “I disapprove of what you say, but I will defend to the death your right to say it.” Mr. Peters writes “There is something fatuous afoot: who would really die to guarantee someone else’s right to speak poppycock?”

His section on Milton might be the best. The author of “Paradise Lost,” he writes, shouldn’t be admired in a free speech context just because he once described a wrestling match between truth and error, with truth winning out. Instead, Milton should be praised because he makes Satan a compelling and persuasive character. By looking fairly and closely at hell, one is tempted by it and gains the strength to combat it.

Unfortunately, unlike Mr. Abrams’s surprising lucid book, “Courting the Abyss” is a slog. Mr. Peters laughs a bit too hard at his own jokes and layers his writing until the reader’s head spins, both when discussing Mill and when dealing with the mundane. “The middle ground seems the most fruitful soil to till, if you can stand the crossfire,” he writes at one point, combining three, maybe four, overlapping cliches into one short sentence. Still, at least Mr. Peters works to describe the tangled roots of free speech, something Mr. Abrams ignores.

If you can only buy one of these two books, and you’re heading out for a relaxing weekend, lay down your money for “Speaking Freely.” If you’re heading for a dank library with a week’s supply of coffee beans, pick up a copy of “Courting the Abyss.”

Mr. Thompson last wrote in these pages about David Boies.