Back in 1975, Robert Nozick was, briefly, famous. Then a 36-year-old Harvard University professor, he made the pages of Newsweek, Forbes and the New York Times with the publication of a tome called ''Anarchy, State and Utopia'' -- a forceful argument against nearly all forms of government coercion, including redistribution by taxes.

As a precocious bigfoot among his colleagues in academic philosophy, Nozick was something of a novelty in the mid-1970s, throwing his weight against the temper of the times instead of pursuing with other philosophers ever more desiccated forms of thought. After briefly flirting as an undergraduate with Students for a Democratic Society in their Port Huron statement days, he swung sharply right as a latter-day disciple of John Stuart Mill, arguing jauntily in his book that a minimal state was all that could be rigorously justified. That put him in a class of people, along with Jamie O'Conner, George Gilder, Martin Feldstein, Janos Kornai and James Buchanan, who fomented the tax revolt along a broad ideological front. The trouble with socialism, Nozick would say, is that it prohibits capitalist acts among consenting adults.

Fifteen years later, much has changed -- including Nozick. What had been controversial in the 1970s became conventional in the 1980s. The wave of changing sentiment that brought Margaret Thatcher and Ronald Reagan to office swept on to Europe, including Scandinavia, most of the Third World, China, Eastern Europe and even the Soviet Union. Today deregulation is the watchword of the world. Meanwhile, Nozick is back, too, with some second thoughts about his earlier attack on the right of the state to coerce people to do good.

His latest book, ''The Examined Life,'' consists of 27 meditations, ranging from ''Dying'' to ''Love's Bond'' to ''Giving Everything Its Due.'' To some, it is high-brow Harold Kushner; to others, philosophically adroit Garrison Keillor; to others still, the book belongs on the shelf beside Marcus Aurelius, Montaigne and Samuel Johnson.

But toward the end of the book, in an essay called ''The Zigzag of Politics,'' he writes: ''The libertarian position I once propounded now seems to me seriously inadequate ... '' Why? ''Because,'' he writes, ''it did not fully knit'' more closely into its fabric ''the humane considerations and joint cooperative activities'' for which the theory had room.

What does this mean? It means the welfare state may be a good idea after all, as an expression of humankind's solidarity with the needy. It's not enough that government have a particular purpose, he writes -- it must have a symbolic meaning, too.

What changed?

Well, from the beginning, Nozick was never quite in sync with the New Conservatism, culturally speaking: He was uncomfortable with Ayn Rand-style libertarianism and National Review politics, he says, and the symbolic neglect of social concerns of the early Reagan years made him uneasy. So he eschewed the think-tank celebrity and stuck close to Harvard.

After an intervening book, ''Philosophical Explanations,'' he turned to writing his meditations on how to live, and so, at least tangentially, to politics. Olin and Scaife Foundation funding gradually dried up as the work progressed; he finished writing ''The Examined Life'' on a National Endowment for the Humanities fellowship.

Nozick shrugs at not being involved with an intellectual gang, but notes that the costs of continuing to speak his mind are real. He writes: ''Once having pigeonholed people and figured out what they are saying, we do not welcome new information that would require us to re-understand and reclassify them, and we resent their forcing us to devote fresh energy to this when we have already expended more than enough in that direction already!''

Presumably what will keep the liberals from pecking him to death is that his theorizing is still exceedingly sharp, his writing program is still unfolding, his second act still looms up ahead.

The new book takes some positions that contrast sharply with the old one. For instance, there is the ''subtraction rule'' he proposes in his essay, ''Parents and Children.'' Nozick doesn't want to rule out parental bequests to children -- they are legitimate expressions of caring about them, he says. But great wealth cascading down the generations doesn't appeal. So, he asks, why not have taxes that would insure that a bequest would last only one lifetime? People could pass only what they earned, not what they inherited. For example: If they inherited $1 million and saved $500,000, they bequeath only the money they made. Perhaps this would be an accounting nightmare with economic consequences that might be difficult to predict. But it's an interesting suggestion, philosophically speaking, from the man who once wrote: ''Individuals have rights and there are certain things no person or group may do to them'' without violating their rights.

Indeed, Nozick cobbles up his own zigzag course toward truth to a full-scale vision of public life. Suppose that there are multiple competing values that no political viewpoint can completely encompass, he says: liberty and equality, love and justice, efficiency and fairness, solidarity and individuality, each entailing a fairly complete political program: Save the whales, a chicken in every pot.

Each political party will select some goals from the list to represent and rank them differently, while giving lip service to all the other possible goals. Some party will gain the ascendancy and go on to build a ''record of accomplishment,'' while the loser searches for a new act. ''The electorate I see as being in the following situation,'' Nozick writes: ''Goals and programs have been pursued for some time by the party in power, and the electorate comes to think that's far enough, perhaps even too far. It's now time to right the balance, to include other goals that have been, until recently at least, neglected or given too low a priority, and it's time to cut back on some of the newly instituted programs, to reform or curtail them.

''The electorate wants the zigzag. Sensible folk, they realize that no political position will adequately include all of the values and goals one wants pursued in the political realm, so these will have to take turns. The electorate as a whole behaves in this sensible fashion, even if significant numbers of people stay committed to their previous goals and favorite programs, come what may. For there may be a significant swing bloc of voters that will shift to new goals and make the difference ... and in any case, a new generation of voters will appear on the scene, ready to seek a different balance, eager even to try something new.''

Robert Nozick remains one of the most valuable early warning systems around, reversing the usual order of things: Having been conservative in youth, he's becoming more liberal with age.

David Warsh is a columnist for the Boston Globe.