Most biographies of literary figures are a wonderful substitute for actually having to read the work. Instead of wrestling with Leaves of Grass, you can speculate about how many bastard children Whitman fathered. Plodding your way through Shakespeare’s Titus Andronicus is for some a less enthralling pursuit than looking into the question of whether its author was a gay Roman Catholic. In the eighteenth century, Dr. Johnson published his magisterial Lives of the Poets; nowadays, it would have to be Sex Lives of the Poets.

Things are different, however, with William Butler Yeats. Because Yeats was a public poet, in a way that is impossible now and was difficult even then, there can be no clear division between the life and the work. This was not true of his English contemporaries. Somewhere between Shelley and Tennyson, poetry in England ceased to be a public affair. As we moved toward the modern age, art, like religion and sexuality, shifted from the public domain to the private one. All three became more like personal hobbies than affairs of state. Penning a lyric, going to church or wreathing your partner in chains and padlocks were now, like collecting beer mats or butterflies, nobody’s business but your own.

Yeats’s Ireland, however, had a venerable tradition of the poet as public figure, all the way from the early medieval bards to the nineteenth-century nationalist literati. For both good and ill, the distinctions between art, politics, religion and culture were less marked on the colonial island than in the metropolitan nation. Yeats spotted with his customary canniness that the post of public bard was still vacant around the turn of the twentieth century. The Irish revolution of independence was stirring, and the movement needed what Gramsci would have called its “organic” intellectuals. The middle-class Anglo-Irish Protestant poet from the west of Ireland applied for the position, so to speak, and was granted it to general acclaim. (In this, he was rather more successful than in his application for a post of professor of English at Trinity College, Dublin, which was turned down on the grounds that he misspelled the word “professor.”) Soon Yeats would be not just poet and mystic but sage, theater director, cultural commissar, public man of letters and clandestine member of the Irish Republican Brotherhood. If the Celticizing, poetic part of him was away with the fairies (an Irish expression for madness), the hardheaded Protestant part took naturally to chairing committees and organizing demonstrations.

The Gaelic Catholic nationalist movement, to be sure, produced a robust intelligentsia of its own, from Daniel O’Connell to James Connolly. But the Anglo-Irish Ascendancy to which Yeats belonged had an honorable tradition of supplying that movement with some of its most distinguished leaders, all the way from Wolfe Tone to Charles Stewart Parnell. Governing classes enjoy more leisure, resources and education than their underlings, and will always produce deviant sons and daughters who hop over the class barriers to put their intellectual talents at the service of the common people. Yeats himself was hopelessly in love with one of those dissident daughters, Maud Gonne, and close to another, Countess Constance Markiewicz.

If this class treachery was generous-hearted, it was also deeply self-interested. Whenever one hears a passionate appeal for unity, of the kind Yeats and his colleagues were accustomed to promulgating, one can usually be sure that somebody’s privileges are being quietly protected. By the turn of the twentieth century, with its landed estates confiscated by the British government and its political power undermined by the nationalists, the Anglo-Irish Ascendancy was more or less washed up as a ruling class. Soon, its big houses would be burned to the ground in the war of independence of 1919-21, an act that Yeats himself thought should be made a capital offense.

Seeking to spearhead the anticolonial movement was in one sense compensation for this loss of power. If this proved too belated and ambitious a project, then the Anglo-Irish could seize cultural rather than political hegemony. Hence the so-called Irish Literary Revival, staffed mostly by Anglo-Irish Protestant artists. Nationalism is a peculiarly poetic kind of politics, full of symbol, vision, myth and rhetoric; and who better to provide the emergent Gaelic nation with the mythologies it needed than renegade poets like Yeats?

These are not the kind of reflections one is likely to stumble upon in Roy Foster’s magnificent biography of the poet, which this second volume brings to completion. For one thing, Foster is not terribly at home with ideas and abstractions. If Yeats had too many of them, his biographer has too few. He is shrewd, pragmatic, civilized and ironic, averse to big pictures and grand theories. This is one reason he is a favored son of the Anglo-Saxon establishment, which likes to think small. Another reason is that, as a commentator on Irish affairs, he tells the British by and large just what they want to hear about the place.

In any case, Foster is himself an offspring of Protestant Anglo-Ireland, and does not intend to be too rude about his eminent predecessors. It is not at all that he is out to whitewash Yeats; he pulls no punches over the poet’s flirtations with Irish fascism (another word the great man couldn’t spell), his fascination with violence, his sympathies for Mussolini’s Italy or his unpleasant eugenic obsessions with stopping the poor from breeding. As with many a Modernist writer, Yeats’s politics were as appalling as his writing was superb, though Foster is not the kind of thinker to whom it would occur to investigate the relationship between these facts. But he is also well aware that Yeats remains a political hot potato in Ireland today, censured by some Gaelic nationalists and wielded as a cultural totem by some of their opponents. Foster naturally wishes to tell the truth as he sees it, but he does not want to provide Yeats’s critics with too much ammunition in the process.

In fact, Foster has scrupulously concealed beneath the suavities of his coruscating prose style an enormous chip on his shoulder. Like the members of many an ousted governing caste, from Malaysia to Zimbabwe, he harbors a smoldering resentment of the native anticolonial movement. Republicanism in his view is less a logical extension of Enlightenment democracy than a bigoted ethnic conspiracy to sideline posh Prods like himself. When an argument touches on this sore point, as Irish arguments often do, he finds it hard to keep his scholarly cool.

There is, for example, a notable difference in tone between his dispassionate treatment of Yeats’s autocratic ideas and ridiculous posturings, and the sneery sardonicism that lurks just beneath the surface when he describes a Gaelic congress or festival. If Gerry Adams had written for himself the kind of breathtakingly arrogant epitaph that Yeats did, one suspects that Foster’s response to it would not be quite so kid-gloved. He writes occasionally of “extreme” politics, meaning those who threaten his own interests. Yeats’s own far-right views are not granted such an epithet.

Like the later Yeats’s, then, Foster’s distaste for Gaelic Catholic nationalism is both understandable and self-centered. Like Yeats, at least in one of his many personas, Foster springs from a distinguished lineage of Anglo-Irish liberals, whose secular bent and coolheaded rationalism put them at odds with the pious redneckery of the Catholic nationalists. (In another of his personas, however, Yeats’s own redneckery was hard even for the Irish Catholic Truth Society to outdo.) The liberal Yeats is the man who spoke up courageously in the Irish Senate for divorce and freedom of thought, just as Foster today insists on thinking outside stereotypes of Irishness.

For reasons both admirable and discreditable, Foster would probably not feel at home in a London-Irish pub, let alone a Boston-Irish one. Irish country houses and London literary dinner parties are where he can relax among his own. The politics of Irish republicanism and antirepublicanism are much more a question of social class than is generally recognized. Foster has a Blairite affection for business schools, but would not recognize an antipoverty campaign if one jumped into his lap. There is nothing in his writing to suggest that wretchedness and exploitation are anything but purely notional realities for him, a lamentable drawback for a historian. When it comes to the turbulent course of Irish history, he has certainly played his part in soft-pedaling them.

The Anglo-Irish, in fact, have been in their day both the mythologizers and demythologizers of the Irish nation. If they are dreamers and eccentrics, they are also caustic, plain-minded and allergic to orthodoxies. Sometimes, Anglo-Irish thinkers like Foster find themselves having to demythologize the myths of precursors like Yeats, as political fortunes change. In Yeats’s day, nationalism seemed to signify a lease on life for this dying Ascendancy breed, and national narratives were accordingly churned out. Nowadays, such mythologizing simply gives comfort to Sinn Fein and the IRA–as, supposedly, do activities like commemorating the dead of the Great Famine, which Foster is on record as deriding. A spot of judicious demythologizing is thus called for, generally known as revisionism. Revisionists like Foster accordingly swap the unity of Ireland for the unity of Europe, Gaelic heroes for Anglo-Irish liberal ones and myths of primitivism for myths of modernization.

Yeats was a mythologizer and Foster is a demythologizer, but otherwise the encounter between them in this book proves remarkably productive. Yeats, who is 50 when the volume opens, becomes an enlightened Irish senator who supervises the design of the coinage that was used in Ireland until recently. He has a rather less enlightened involvement with the Irish Blueshirts (the fascist movement), speaks up for a cultivated despotism, turns out some of the finest poetry of the twentieth century and receives the Nobel Prize in Stockholm.

At the beginning of the book, he has married “George” Hyde Lees and is receiving supernatural messages through her trancelike writing. These stem from a group known as the Instructors, who inform the poet that the child with whom his wife is pregnant will be the Avatar whom the world needs for its salvation. (The son in question is still alive, but so far has shown no signs of any plan to assassinate Bush.) Few great writers have been so well and truly off the wall as Yeats, though Foster rather stiffly refuses to concede that he could be extraordinarily silly. By the end of the volume, the poet is worried about his sexual potency: A visit to a brothel, so he confides, was “like putting an oyster into a slot machine.” He undergoes an operation to restore his virility, and dies greatly perturbed by the “filthy modern tide” and the degeneracy of the modern age.

W.B. Yeats: A Life is a formidable scholarly achievement. The research that informs it is staggering; its critical dissections are delicate and acute; and its supple, lucid prose is splendidly stylish. There are some marvelous cameos, like his one of Lady Ottoline Morrell: “Tall, soulful, still eccentrically beautiful at forty-five, she decorated both herself and her house in a high style, where gypsy-chic met mock-medieval splendour.” Grippingly readable and intellectually rich, the book is without doubt one of the mightiest biographies of our age.

It therefore seems almost unspeakably churlish to inquire, after its author’s seventeen years of devoted labor, whether it is really necessary. Do we really need an account of anyone in this kind of detail? Even Jesus Christ was granted nothing like this word length. No doubt some scholar will find it useful to learn that when Yeats moved house, “a phone was duly installed within ten days. Pictures were hung, the garden began to exert a spell, and he resumed playing croquet.” For the less erudite among us, this is just a little more information than we needed, as Uma Thurman remarks to John Travolta in Pulp Fiction when he reports on his visit to the bathroom.

If Foster’s project is vastly ambitious, it is in another sense too modest for its own good. Like a well-groomed BBC reporter, Foster confines himself for the most part to documenting his author’s daily life with a minimum of critical commentary. Like many a biographer, he fails, or deliberately refuses, to step back from the trees to survey the woods. This self-denial is a major loss. Because of it, one’s judgment on the whole heroic enterprise must inevitably be ambiguous: C’est magnifique, mais ce n’est pas nécessaire. This, however, will not be the general judgment of the critics, who will lavish praise on the book not only because it richly deserves it but because its author is incapable of entertaining an opinion that falls outside their own cozy liberal consensus.