COMMIES: A Journey Through the Old Left, the New Left, and the Leftover Left, by Ronald Radosh. Encounter. 216 pp.

One curious effect of the Reagan era upon political discourse was to introduce the expression "Shachtmanite" into the Washington pundit's vocabulary, however briefly and imprecisely. This was a term from the Depression-era cafeteria feuds of New York's City College, referring to a particular species of revolutionary for whom the Soviet Union represented not merely the betrayal of socialist principles but a complex historical problem, to be solved through the correct application of the Marxist algebra. In 1928, Max Shachtman had been one of the three original American communists expelled for the crime of Trotskyism. When he died in 1972, he had worked out a rationale for why the labor movement should support Richard Nixon against George McGovern. Such performances by a skilled dialectician can be wonderful to behold.

A lot of neoconservatives had been Shachtmanites. But Max, for all his hostility to the totalitarian left, reserved a special contempt for former radicals who peddled their disillusionment on the open market. He once dismissed the memoirs of several ex-communists by saying that they were composed by a formula: "Once I was so stupid, now I am so smart." In the Shachtmanite world, a certain degree of rigor was required: Confession minus analysis equaled bourgeois self-indulgence.

It all seems so long ago. A few of us still use expressions like "Shachtmanite" and "Stalinoid," of course, just as there are people who can, when the need arises, write in cuneiform. It is a world well lost. But the occasional sectarian refugee still wanders the earth in a daze of denial, looking to pick an argument, even if that means he ends up talking to himself.

Ronald Radosh, a former radical intellectual who now writes for conservative publications, is very much a product of the Old Left, though he spent a while in the trenches of the New Left as well. His memoir Commies is a historical artifact. Perhaps literally so: The manuscript might well have been stored in a vault for 10 years. Or 20, or 50. It has the texture and dusty aroma of something mummified.

The transformation of an ardent left-winger into an ardent right-winger is a tale often told -- but rarely with so little conviction of the story's urgency or contemporary relevance, nor, indeed, with so much merely personal grievance, standing in where a candid examination of motives ought to be.

Radosh was what radicals call a "red-diaper baby." He grew up in a fellow-traveling household, went to communist-run summer camps, and during college was active with the Labor Youth League, which by the 1950s was what the Young Communist League preferred to call itself. He sang folk songs and went to demonstrations, and he served as an emissary from the old Sovietophiliac radicalism to the brilliant circle of young intellectuals around the journal Studies on the Left in Madison, Wis. Amid the upheavals of the counterculture, Radosh rebelled against authority in his own way by embracing the work of Isaac Deutscher, Trotsky's biographer. (Deutscher had been an anti-Stalinist, but he expected great things of the Khrushchev reforms.)

During the late 1970s, Radosh began doing research into the Rosenberg case. In 1983, he published The Rosenberg File, which argued very persuasively that, as charged, Julius Rosenberg had been part of an atomic spy ring. Subsequent evidence from the Soviet archives strongly corroborates this judgment, but it still causes much grief to true believers of a certain age. According to Radosh, the harsh criticism that book attracted was a turning point for him.

He had been willing to temper his criticism of "actually existing socialism" during the Soviet invasions of Hungary, Czechoslovakia and Afghanistan. But when American leftists began to snub him, it was time for a reckoning. The memoir is at its most interesting when he describes his warfare in the salons of New York -- a reminder that, as Saul Bellow's character Ravelstein reminds us, one era's gossip is another's social history.

In the 1970s, Radosh had made an uneasy alliance with socialist intellectuals such as Irving Howe and Michael Harrington -- former protege of Max Shachtman, men quite capable of holding their own in a political argument. (The Marxist god of History had given them that, mainly, to do.) They saw the radical project in America as a matter of pushing liberal democracy as hard as possible rather than replacing it with some streamlined authoritarian regime. This circle had no illusions about the innocence of the Rosenbergs. But from Commies it is clear that they always harbored serious misgivings about Radosh himself. No doubt they suspected that habits of thought cultivated while rationalizing brutal regimes of one sort are really very helpful when one shifts allegiance to thugs of a different political complexion.

If so, their misgivings were borne out. Radosh soon became a champion of the terrorist Contras in Nicaragua, cheering them as a genuine army of the people. More recently, in the course of research on the Spanish Civil War, he has discovered the virtues of General Franco -- a fascist dictator, yes, but at least no communist.

At this point, it would be routine to cite the Cold War anthology The God That Failed (1950) -- perhaps with a sneer, which is the preferred attitude toward the book adopted by soi-disant leftists who have never actually read it. But there is really very little resemblance between Commies and the essays of ex-communists such as Arthur Koestler or Richard Wright. Something is missing: the element of soul-searching.

Nothing in Radosh's memoir conveys the painful ordeal of dis-illusionment, in the strong sense: an ordeal, a crisis in which one faces not only the morally repulsive consequences of beliefs and actions but also the qualities of willful self-deception and ideologically compulsory blindness that have sustained one's previous commitments.

Instead, we get a chronicle of complaints and alibis. It is a commonplace that leftist dogma can be a way to avoid unpleasant realities about oneself. Commies makes a pioneering and rather daring use of right-wing rhetoric for the same end. When Radosh's first (and by his own account quite miserable) marriage finally disintegrates, this is because his wife was influenced by the women's movement. A few pages later, he finds himself having sex with an alcoholic girlfriend on top of Mount Rushmore. "I now don't understand why or even how I did such things," he writes. "Perhaps it was the cumulative effect of too much marijuana." So much for personal responsibility. It was all the Zeitgeist's fault.

Maybe he's right. Radosh's memoir, while full of anecdotes that will entertain those of us who can't get enough of this sort of trivia, lacks the force of conviction that comes from finding a new principle for understanding the world or one's life. In that regard, it is "post-ideological," as the self-defining pundit term of the era has it. All passion spent, and so forth.

There are levels of political reality not registered by that cliche. In the wake of Bill Clinton, some conservative activists have given up hope for American culture; meanwhile Antonio Negri, an Italian theoretician of the extreme left, has embraced the U.S. Constitution as a framework for revolutionary strategy in the era of globalization. Ideology isn't dead, it's mutating wildly. But a scrapbook of grievances from days gone by won't teach you a thing about the world we are facing.