he strength of poetry, as James Fenton perceives it, depends on the weaknesses of poets. His lectures on 20th-century writers from Wilfred Owen and Marianne Moore to Sylvia Plath and Seamus Heaney are tributes to the quirks and confusions, the willfulness and oddities, that shape each poet's unique voice. By embracing what Fenton describes as humiliations and failures, by refusing to calculate their way to success, these poets release themselves to write in ways that speak to their readers, as they could never do by putting on a conventional show of strength.

Fenton's book comprises 12 of the 15 lectures he delivered in his five-year term as professor of poetry at Oxford -- probably the world's only academic chair whose occupant is chosen by a quasi-public election. The results make the front page in British newspapers, and the three annual lectures required of the professor are advertised to the public. Fenton knows how to address a wide audience: he has worked as a reporter in the Philippines, Borneo and the Houses of Parliament, as a gardening columnist and as a theater reviewer. His own poems are written with edgy precision, metrical virtuosity and a memorably unsettling mixture of the ordinary and the ominous.

In his opening lecture, but less often afterward, Fenton's tone sometimes turns slangy, jokey or abrasive. He imagines Michelangelo thinking of a younger artist as a ''Flemish twerp,'' Coleridge sending Wordsworth ''up the wall,'' a phrase he also applies to D. H. Lawrence's effect on Lawrence's wife, Frieda. It soon becomes evident that this tone is the product of shyness, not aggression. Fenton is warding off the cynical disdain of an Oxford audience that probably will not want to hear about the psychological vulnerabilities it might have in common with the writers whom Fenton is about to discuss.

Fenton is skeptical of the ''handy teleologies'' of much recent criticism, in which poems are seen as the product of large historical forces rather than the personal idiosyncrasies of poets. He was probably confirmed in his skepticism by his years as a reporter. His second lecture, on Wilfred Owen, finds a more complex and idiosyncratic story hidden in the standard account in which Owen abandons the Victorian style of his youthful poetry because he had been ''shocked into the 20th century'' by the experience of trench warfare. Fenton notices that Owen, just before his death in 1918, was planning verse dramas in the Tennysonian style that he had supposedly abandoned, and that he was still writing Victorian verse in the worst days of the war. The bleak modernity of Owen's greatest poems has more to do, in Fenton's version, with private events that released Owen from sexual guilts that he had disguised and explored under the cover of his archaic style, and with Owen's sense that his war poetry was only a detour from his long-term intention to write blank verse on old Welsh themes and, as he called them, ''Idyls in Prose.'' As in all of Fenton's lectures, the effect of the argument is to make Owen's poetry more moving, because more personal, more particular, than it had seemed before.

''There is no such thing as the artistic personality,'' Fenton says in his opening pages, ''not in poetry, not in the visual arts.'' His theme throughout the book is the way in which art is inseparable from personal uniqueness. Philip Larkin, he observes, is widely admired for expressing common experience, but what is most striking about Larkin ''is not the commonness but the singularity of the point of view.'' Three lectures on Marianne Moore, Elizabeth Bishop and Sylvia Plath focus on the divergent ways in which they refused the conventionally radical and traditional roles available to a woman poet. Almost the only poems by Seamus Heaney that Fenton doesn't admire are those in which Heaney, borrowing the glamour of someone else's oppression, tried to write ''as if living under an Eastern European censorship.'' A poet's uniqueness is not a quality that can be sought; writers who try to sound unique end up by sounding like some other writer whose uniqueness they envy. Fenton recognizes that a ''fertile weakness'' can be more productive than strength. For the hero of his book (the subject of three lectures to everyone else's one) he chooses W. H. Auden, for whom any good poem could be ''a source of strength'' because he had no wish to pit his strength against that of others.

Fenton is most impressed by poets when they are least impressed by poetry, especially their own. Wilfred Owen wrote his best poems when he was distracted from the timelessness of art by ''an important task in the here and now: the task of warning and being truthful about the war.'' D. H. Lawrence, at his poetic best, ''isn't interested in art. But he is interested in freedom.'' Marianne Moore famously wrote, ''There are things that are important beyond all this fiddle.'' Fenton admires her for the sense of civic and religious duty that led her, when young, to teach in a school for American Indian children, and that continued to gave shape and style to her poems. He closes his book with a soaring defense of Auden's distrust of the powers and pretensions of art, his refusal of his own rhetorical powers, his ''forward impulse of renunciation.''

This conclusion may seem to have little connection with the opening pages, where the subject of modern verse is introduced with episodes from the lives of Florentine sculptors. But ''The Strength of Poetry'' has a taut and satisfying shape that serves its overall argument. The first lecture echoes the fashionable academic technique of arriving at one's real subject after describing an exotic event that occurred thousands of miles and hundreds of years distant from it. This method is typically deployed in order to expose a hidden political agenda in, say, ''The Winter's Tale'' or ''The Turn of the Screw.'' Fenton has a different purpose. He uses his anecdotes as parables, stories about different ways in which you can choose to live your life. By his sixth page, he has begun talking about everyone's wish to evade the sufferings that go with failure: ''But for a productive life, and a happy one, each failure must be felt and worked through. It must form part of the dynamic of your creativity.''

Critics of modern poetry divide into two categories: aesthetes and moralists. Aesthete critics focus on craft and technique while tending to dismiss anything that a poem might have to say. Moralist critics, including Fenton, value poetic technique but are equally moved by a poem's content and are excited by its ideas. In one of Fenton's characteristic asides, after describing a poem by Larkin as ''a poem of feeling rather than thought,'' he adds, ''I would be happier with it, though, if its thoughts were clearer.'' For the aesthete, poetry is a means of escape from the complexities and pain of reality. For the moralist, one of the central functions of poetry -- as the critic Harold Rosenberg once said about art -- is ''to keep reality on the agenda.''

At least two reviews of Fenton's book by aesthete critics in Britain and America have displayed a vindictive rage out of all proportion to any imaginable offense. Intellectual fury generally seems to be a form of defense against intolerable knowledge, and it is striking that Fenton's use of parable seems to outrage the reviewers most. What is it that they so urgently want not to know?

Fenton displays anger only about political issues like imperialism, and, having reported from wartime Vietnam, he has seen a lot to be angry about. He is coolly ironic when he detects imperialist motives in T. S. Eliot's worst poem, ''To the Indians Who Died in Africa.'' But his anger flares when he excoriates Robert Frost for having written the ''egregious rubbish'' of ''The Gift Outright'' when he felt the urge to ''to assert the arrival of a new Augustan age.'' Frost ''spelled out'' that urge, Fenton continues, in a companion poem that proclaimed John Kennedy's presidency as ''A golden age of poetry and power.'' But ''The Gift Outright'' had in fact been written 25 years before Kennedy was inaugurated, and Frost first published it a few months after the United States entered the war against Nazi Germany in 1941 -- a historical context that gives a different flavor to the poem's patriotism. Fenton's error illustrates that although anger is almost always illuminating in political writing, in literary criticism it is almost always mistaken.

Elsewhere in the book, Fenton argues with poets he admires, but never stops admiring them, and the effect throughout is of a series of passionately intelligent conversations between critic and poet. In its bracing and sympathetic readings of poets as various as Bishop and Plath, or Lawrence and Auden, ''The Strength of Poetry'' exemplifies the inherent generosity of intelligence.