ROBERT NOZICK made his name with a book which took anarchism seriously and ended by suggesting, as a rational alternative to it, a theory of the minimal state--the state committed solely to the protection of life, liberty and property. He has now followed up his Anarchy, State and Utopia (1974) with a book which takes skepticism seriously, and offers a tentative and speculative metaphysics, which at least finds a place for free will, personal identity, moral judgment and aesthetic experience.

Nozick has often been compared to the 17th-century Whig philosopher John Locke, if only because he builds his political theory on a vindication of individual natural rights (which he calls "entitlements"), including the right which Locke felt it most necessary to justify-- property (which Nozick calls "holdings"). And like Locke, Nozick has suffered the fate of being treated as an ideologue, a champion of the interests of the property-owning classes, which is altogether unfair, since both Nozick and Locke are philosophers writing philosophy, defending an abstract right to property as they themselves define it.

Nozick pleads for a natural entitlement to possess justly earned or justly transmitted "holdings," which may or may not correspond to "property" as that concept is defined by lawyers and legislators. People who speak of Nozick as "right-wing" are those who do not reflect enough on the ambiguity of the word "property."

Even so, the ideological perspective seems inescapable. In Jeffrey Paul's collection of essays by several authors, Reading Nozick, most of the criticisms of Nozick's political theory fall into one of two classes: either he is said to be too much the anarchist or to be too little of an anarchist. Either he is reproached for justifying the existence of the state, or for denying the use of the state for purposes of social security and welfare or redistributing possessions. No one seems to like the idea of a minimal state; yet Nozick makes such an effective case for it that angry voices are heard on all sides.

Of his new book, Philosophical Explanations, the first question that is bound to be asked is: is it consistent with, and does it fortify the case made in his first book? Locke, with his Essay on Human Understanding, failed notoriously to sustain the natural law theory of his Treatise on Government, and even undermined it with its invocation of empiricism. Does Nozick do any better?

Well, he does not do worse. The principle of liberty, which is so central to Nozick's political theory, is also central to his metaphysics. He wishes to show that we are free in the sense of having a free will as well as in the sense of having a natural right to political liberty. He seems to feel that if determinism were true and if human life were a long chain of causes and effects, there would be no ultimate basis for the libertarian case. Only if we are capable of choosing can one claim that we should be allowed to choose. This is why Nozick fortifies his old plea for an entitlement to freedom in politics with a new defense of freedom as a metaphysical reality.

Nozick refuses to engage in the kind of philosophy which aims to provide a knock-down argument, to command assent or compel agreement. All this is far too aggressive and dictatorial for Robert Nozick. He does not want to force anyone to believe anything. He simply wants to suggest explanations, and that is the activity he calls philosophy. The explanations he puts forward in his Philosophical Explanations are, as he says, not advanced "as the sole correct view on their topics, but as members among others of admissible classes, with the hope that they will be ranked first, or at least highly."

One cannot fail to admire Nozick's refusal to bully; for it is a melancholy fact that many philosophers, especially liberals, really are bullies. His method, he claims, is one of suggesting, but it might be truer to say that it is the method of charming. The reader should perhaps beware of being seduced by such an unfailingly attractive writer. For example, Nozick's whole treatment of the foundations of ethics is conducted in the language of "value," which enables him to pass very elegantly to a discussion of the meaning of art and of life itself. Harsh words, such as "duty," which ought to be at the forefront of any theory of ethics, are hardly ever uttered. Admittedly "retribution" and "punishment" are discussed, but only in the context of the problem of free will, and even then, we are carried to the reassuring conclusion that "punishment not only is not central to the problem of free will, it is not derivative either." This helps one to forget retribution and punishment, and move on to thinking about beauty, truth and goodness.

The whole book ends on an almost elegiac note: "We can envision a humanistic philosophy, a self-consciously artistic one, sculpting ideas, value, and meaning into new constellations, reverberative with mythic power, lifting and ennobling us by its content and by its creation, leading us to understand and to respond to value and meaning--to experience them and attain them anew."

Clearly, Nozick has moved much further from skepticism in philosopy than he has ever moved from anarchism in politics. And for all his modest demeanor, he has nothing like Locke's modest conception of philosophy as an exercise confined to clearing away the rubbish that lies in the path of knowledge. Philosophical Explanations establishes his identity as a constructive metaphysician, a theorist with a style and a method of his own, and ideas as bold as they are bright.