BOOK REVIEW : Censorship: Hushing the Voices of Dissent : FREE SPEECH IN AN OPEN SOCIETY, <i> by Rodney A. Smolla,</i> Knopf, $25; 464 pages

“Freedom of speech is a human yearning--insistent, persistent and universal,” declares Rodney A. Smolla, attorney and law professor, in “Free Speech in an Open Society.” But it’s equally axiomatic that law is the natural enemy of free speech.

“Censorship is a social instinct,” he points out. “Governments in all places at all times have succumbed to the impulse to exert control over speech and conscience.”

The war between these two opposing human impulses--the voice that speaks out and the voice that hushes--is the real concern of Smolla’s book, a scholarly work that goes beyond the platitudes of the debate over the First Amendment.

Indeed, Smolla’s book is an exercise in moral, intellectual and jurisprudential model-making, an effort to deconstruct the mechanisms of censorship and reveal the inner workings of the First Amendment.

The law that criminalizes the burning of flags and draft cards, as Smolla allows us to understand, is not different in kind from the law of copyright or defamation or trademark, all of which amount to walls around the First Amendment. In that sense, “Free Speech” is a blueprint of the chinks and cracks, the windows and doors in those walls.

Smolla is no First Amendment absolutist, but he is an unabashed advocate of free speech, and--at times--he is given to the magisterial prose of the philosopher and the moral ecstasies of a preacher. “Freedom of thought, conscience and expression are numinous values,” he booms, “linked to the defining characteristics of man.”

He’s a lively, even whimsical writer--especially considering his own training and the subject of his book--and he livens up the proceedings with little bursts of high-toned rhetorical tap-dancing: “The Texas v. Johnson case,” he writes about a recent Supreme Court case on flag burning, “was an intellectually and emotionally intense cliff-hanger, in which John Stuart Mill beat Aristotle 5-4.”

To his credit, Smolla goes beyond the ordinary fire-in-a-crowded-theater stuff and ponders “hate speech,” public funding of the arts, political advertising, the death sentence against Salman Rushdie and the Persian Gulf War--”the first prime-time live television war.”

As a result, there’s an edge and an immediacy to his work, a sense of what really counts in the debate over free speech.

Still, “Free Speech” is essentially a book about law--and, the reader must be warned, the philosophy of law. As a result, the text is sometimes dense and weighty, and Smolla never quite succeeds in purging his book of the catch phrases favored by law professors and appellate judges.

Thus, we are invited to ponder the “the fulcrum of affiliation,” “the proportionality principle,” “the reasonable nexus standard” and “the theory of hate speech as a relational harm.”

Smolla dresses up the book with lots of charts and graphs, including a “Proximity Diagram for Clear and Present Danger” and something that he rather charmingly calls “The Harms Chart.”

At its heart--and here is one law book with a big heart--”Free Speech in an Open Society” exhorts us to overcome the dark fears that prompt us to punish the dissenting voice.

And the price of fear, he suggests, is a shrill and disabling paranoia that manifests itself not only in the censor’s blue pencil but in the very health of our democracy.

“Men feared witches and burned witches,” he writes, quoting Brandeis. “It cannot be said often enough.”

Next: Richard Eder reviews “Primitive People” by Francine Prose (Farrar Straus and Giroux).