THIS BOOK collects some of the most eloquent and subtle literary essays written in English in the past 10 years. They are the work of a poet who began writing in English 10 years ago, after teaching himself to read it a few years earlier in a Siberian labor camp. Joseph Brodsky, like Joseph Conrad, writes flawlessly in a language he learned in exile. Only an occasional oddity in Conrad's syntax hinted that he sometimes thought in some other language while writing in English; only Brodsky's pleasure in puns and verbal echoes hints that he still sees the English language as an exotic garden of delights. His prose has the energy and precision of a master, and, at times, the moral authority of a prophet.

Most of the essays in Less Than One concern 20th-century poetry in Russian and English, but the book is framed by two memoirs of his childhood in Leningrad. The political passions of these memoirs inform everything else in the book. (As Conrad's homeland was ruled by the czar, so Brodsky's homeland is ruled by the czar's successors.) The school where every morning Brodsky "prepared himself to hear drivel" and the factory where he worked afterwards seem to be two versions of the same institution, each justified by the same lies. Later, when Brodsky was convicted of "social parasitism," prison seemed the same institution in yet another form. In a world in which no one could learn responsibilities, he developed the fear that he might be unequal to any task at hand, that he could not act as a unique person -- in short, that "one is perhaps less than 'one.' " Now, he implies, he continues to feel that he can write as a unique and individual "one" only by constant acts of resistance and assertion.

Brodsky uses the same language to describe the act of writing a poem and to describe the act of resisting the state. Like Goethe's Faust he regards freedom not as a state of calm but as the product of unending struggle -- more precisely, as the struggle itself. For Brodsky, formal verse is the only kind worth writing, precisely because rhymes and stanzas are as limiting and intransigent as a police state. A poet wins success only by resisting the featureless anonymity that regular forms would otherwise impose. In an age of avant-garde experiments, Anna Akhmatova (the subject of one of Brodsky's most eloquent essays) chose to work within the conventions of classical forms, but she "sounds so independent because from the outset she knew how to exploit the enemy."

Exploiting the enemy is Brodsky's preferred technique in politics as in literature. In a commencement address -- one of the rare examples of that genre worth reading -- he recalls a labor-camp inmate who performed so extravagant a display of overwork that the guards were too embarrassed to demand more. As Brodsky points out, the gospel verse that urges you to turn the other cheek is more than an instruction to return good for evil. The verse goes on to urge you to give your cloak to the thief who takes your coat, and to go two miles when you are compelled to go one. "The meaning of these lines," Brodsky writes, "is anything but passive, for it suggests that evil can be made absurd through excess."

In the same way, the density and complexity of great poetry make absurd the arbitrary limits of form and meter. Brodsky's poetry, like his politics, is built on "the hope that the victim will always be more inventive, more original in his thinking, more enterprising than the villain. Hence the chance that the victim may triumph." Hence the triumph of the poets he admires.

BRODSKY'S vision of oppression and resistance is the source of both the major strengths and the minor weaknesses of this book. He has devoted a lifetime to the search for ever more ingenious means of revolt, ever more creative ways of using power against itself, and no critic has a wider and more active understanding of the ethical implications of poetic language. His essays on Russian writers -- Dostoevsky, Akhmatova, Nadezhda Mandelstam, Marina Tsvetaeva, Andrei Platonov -- convey even to a reader who knows no Russian the moral force of the choices reflected in their vocabulary and their grammar. His essays on Western writers -- Eugenio Montale, Derek Walcott, W.H. Auden -- are equally committed and convincing. Brodsky makes an equation between the sharpness of a poet's ethical instincts and the keenness of the poet's ear. He proves the equation in a pair of breathtaking essays that analyze, syllable by syllable, a single poem by Tsvetaeva and a single poem by Auden.

Both these essays are extraordinary in their combination of detailed literary understanding with concerned ethical intelligence, but the essay on Auden's "September 1, 1939" is a special triumph. Brodsky can hear precise gradations of tone in his adopted language, and he can draw moral parables from patterns of rhyme. He reports that when he began writing English prose, his "sole purpose then, as it is now, was to find myself in closer proximity to the greatest mind of the twentieth century: Wystan Hugh Auden." Few critics have achieved such proximity to the mind and art of any author.

Yet Brodsky is so powerful a critic that he can transform his subjects into versions of himself. Without recognizing that he is doing so, he praises Auden's poem for the same reasons that Auden eventually renounced it. Auden saw the poem as "infected by an incurable dishonesty," in part because he saw it as a poem in which he manipulated language for his personal ends rather than as a poem in which language had a chance to speak for itself. For Auden, a successful poem was a hymn of praise to the language in which it was written. For Brodsky, a successful poem is a cunning act of resistance against a language that tries to exploit the poet as its own instrument. He finds the "millennarian" fantasy of Communism "embedded" in the Russian language, and he honors the novelist Andrei Platonov for attacking "the very carrier of millennarian sensibility in Russian society: the language itself."

Throughout this book Brodsky is on the attack. A densely speculative essay on Byzantium keeps modulating into an attack on Russian tyranny; an evocation of Leningrad makes uneasy distinctions between the imaginative tyranny of Peter the Great and the dull tyranny of the Communist Party, and ends by attacking both. But Brodsky is not entirely happy with his own stance. He rebukes dissident Russian writers for attacking only those forces that are outside themselves -- very much as he seems to do in his own work. "No matter how poisonously sarcastic one gets, the target of such sarcasm is always external: the system and the powers-that-be." He notes that Auden, in contrast, never applied a pejorative term to others without also applying it secretly to himself. Brodsky has in fact adopted Auden's method as his own, and the ethical drama played out within his essays -- a drama in which he argues as eloquently with himself as with his enemies -- has all the intricacy and depth of an enduring work of art.