A double helping of sage

John Ruskin: The Early Years by Tim Hilton (Yale £10.95) and John Ruskin: The Later Years by Tim Hilton (Yale £20)

Ruskin enjoys high name-recognition. He's up there with other premier division Victorians: Dickens, the Misses Brontë, Trollope, Eliot, Carlyle, Tennyson, Macaulay. But, should conversation lag at your Hampstead dinner party, try the following parlour game - name three major works by Ruskin. The modestly literate will probably come up with Modern Painters and Stones of Venice. Then, what? Munera Pulveris, Unto this Last, Fors Clavigera, Sesame and Lilies, Ethics of the Dust, Praeterita, Love's Meinie.

You'd need to be PhD literate to give some account of those books, or even to translate the titles into comprehensible English. Tim Hilton, who has spent a lifetime working with Ruskin and considers the work his masterpiece, cannot tell us what Fors Clavigera means ("truth of the nail" is the best translation - but what the hell does that mean?). And if Dickens is a novelist, Macaulay a historian, and Tennyson a poet, what, precisely, is John Ruskin? An art critic? An artist? A literary critic? A belletrist? A sublime gasbag?

Best is the cover-all term "Victorian sage" - the voice of his age. No voice was more powerful. Ruskin himself bemoaned seeing his exquisitely wrought aesthetic views grotesquely reflected back at him in the gimcrack Venetian brickwork, Norman architraves, and Gothic ornamentation of every newly built villa and terrace he passed in south London - particularly the speculative building that defaced the beautifully rustic Herne Hill of his childhood. If you want Ruskinian monuments, look around you at the wastelands of SE24.

The lineaments of Ruskin's life are well known. Of all the Victorians, he bears out the truth of Dryden's maxim, "great wits are sure to madness near allied, and thin partitions do their bounds divide". Little John was brought up the pampered child of a Scottish sherry merchant enriched by the new fashionability of the Spanish apéritif. Amazingly precocious from childhood, the young prodigy was educated at home, forced into genius like a hothouse orchid. He was publishing poems in his teens and displaying artistic talent. When he went to Oxford (inevitably) his mother came with him. Damagingly - disastrously, as it eventually turned out - he was kept from distracting intercourse with fellow students or the opposite sex. Emotionally, he was never allowed to grow up.

As an undergraduate, and under the stimulus of his early visits to Italy, Ruskin embarked on his magnum opus. The first volume of Modern Painters came out when he was 24 (in true Ruskinian style, it has little to do with modern painters). Like Byron, he woke to find himself famous. Writing, Ruskin realised, was power - "his instrument, his sword".

He used his fame to promote the man he considered the greatest artist of his time, J M W Turner, and, in the broader sense, to educate his age aesthetically and morally. As a first step it meant instructing them in the glories of painters of the Renaissance (principally Fra Angelico and Tintoretto). Later, Ruskin realised that a whole new ethic needed to be forged. Victorian values, that is. Like Kingsley, F D Maurice and Morris, he became one of those strangely English - non-Marxist - utopian-socialists. His influence can be felt in Blairite "Christian Socialism".

Always neurasthenic and hypo-chondriac, Ruskin married in his late twenties an eminently suitable young Scottish woman chosen for him by his guardians. The union was never consummated. Later, a spiteful Effie recorded that on the wedding night John proclaimed himself "disgusted with my person". Hilton inclines to the explanation that Effie was menstruating. Ruskin may have been impotent (the grounds on which the marriage was eventually annulled). He himself protested that he was indeed virile - proof of which was his indulgence in the "vice of Rousseau" (self-abuse, that is). He probably died a virgin.

Six years after the marriage, Effie eloped with John Millais. She bore the modern painter eight children and prosecuted a lifelong grudge campaign against her first husband. Despite the humiliation, Ruskin continued to forge his unique combination of moralism, art-historical research and aestheticism into resonant works of high literature of which the most enduring is The Stones of Venice (if you would understand the art of Tintoretto, the argment runs, you must examine the material foundations it rests on).

The personal complexities of Ruskin's life were never solved. In his late forties, he conceived a violent passion for a teenager, Rose La Touche. He offered her marriage; the maiden accepted, with the proviso that he wait till she was 21. Age difference apart, Rose was a religious maniac and an anorexic (as Hilton surmises). A "hunger artist", she seems to have starved herself to death. Ruskin, his heart blasted, soldiered on. The youthful prodigy of 1843 was now, as witnessed by his libellous attack on Whistler in 1877, the old guard. In his last 10 years - horribly painful, even in Hilton's restrained account - he descended into incapable madness, tormented by what he called the "plague winds" of his imagination.

Tim Hilton gave us a first volume, dealing with the first 40 years of Ruskin's "brave, unhappy life", 15 years ago. The narrative is crisp and lively. Hilton expertly digested the massive primary materials: acres of correspondence (most of it manuscript) and published writing. The Library Edition of Ruskin's works (of which Hilton is very suspicious) runs to 39 volumes and is incomplete.

Hilton's second volume, dealing with the last 40 years, is twice as long as its predecessor (it was in draft, as the preface tells us, twice as long again). It is markedly different in tone. The first volume was infected with Ruskin's youthful brio, the second is as sombre as a requiem. Rather than digest Ruskin's writing, Hilton quotes extensively, often at page length. The hugeness of Ruskin's achievement is respected. But the reader is made to work. This is a biography which has been hard to write; the biographer will not make it easy to read.

Controlling both volumes is Hilton's expertise as an art historian (he is, as long-time readers of this paper will know, one of the greatest we have). There is also the familiar, in-your-face, Hilton bluntness. This is how he deals with his subject's psycho-sexual pathology: "Ruskin's sexual maladjustment is not an uncommon one. He was a paedophile. He is typical of the condition in a number of ways, for paedophilia generally emerges in his age-group, often follows a period of marital breakdown, and in old age is accompanied by (or is a palliative to) a sense of loneliness and isolation." There is no hint of moral condemnation. Indeed, Hilton seems to see the vice of Gary Glitter as so common as to warrant tolerance. It is a price to be paid for the writing. Lucky Ruskin that he died before the tabloid newspaper era.

It's presumptuous of a reviewer, in possession of a book for a few weeks, to pass judgement on a work of scholarship which has taken the best part of a scholarly lifetime to write. But Hilton's Ruskin, if any biography does, merits the description "authoritative". And, different as they are, the volumes should be taken as a double dose.