In a recently discovered sketch, Rose La Touche, the 24-year-old lover of John Ruskin, lies on her death bed. Her hair is spread out on the pillow like some latter-day Medusa; her eyes stare at the artist - her fitfully requited inamorata - from a gaunt, pale face. This startling drawing, more redolent of Egon Schiele than some sentimental Victorian picture, vividly records the young woman's demise in 1875, probably from anorexia. It is difficult to reconcile this image with the fresh-faced young girl whom Ruskin first met when she was 10 years old and he was 39. The distance between the two lovers - the two Roses - seems an impossible divide. Yet it is one that symbolises Ruskin's extraordinary journey, from stern Victorian critic, social reformer and shaper of the pre-Raphaelite aesthetic, to spiritualist, visionary and, eventually, madman.
In January 1858, the La Touches, County Kildare gentry of Huguenot descent, asked Ruskin to teach their daughter to draw. Ruskin's first impressions of Rose, as she visited him at his London home in Denmark Hill were suffused with pre-Raphaelite iconography - or, perhaps more darkly, echoes of Lewis Carroll's fantasies - as she "walked like a little white statue through the twilight woods, talking solemnly". She was the incarnation of untouchable mystery, and over the next decade and a half, Ruskin sought to capture her on paper, if not in the flesh; from the innocent girl who called him "St Crumpet", to the grown woman whose profile he drew in a classical cameo. Yet his idealised vision of Rose seemed to grow fainter as she ailed - assailed by her evangelist parents, who opposed the relationship; by Ruskin, who would never take no for an answer; and by his former wife, Effie (now married to John Everett Millais), who attested to Ruskin's "unnaturalness" and inability to perform on theirwedding night.
The result was mind-numbing pain. " Everything hurt me," Rose wrote, in an account that itself seems to ache, "I seemed to think through my head ... I can only say again - I seemed to hurt myself." The contemporary Ruskinian, Tim Hilton, sees in Rose not only the arrested sexual development that anorexia can induce, but also a disturbing suggestion of abuse by her father. But Maria La Touche saw her daughter's condition as psychic, as if illness already bound her to the other world. "I think he wants to see me," Rose would say of Ruskin, telepathically. And while her doctors diagnosed hysteria, a condition "most prevalent in the young female members of the higher classes", they also discerned that excited minds seemed "to exercise some mysterious or occult influence". It is also clear, from letters I discovered while writing my book, that Rose wanted to hurt herself. "Oh how gladly I would close my quarter century," she told her confidante, Georgiana Cowper. At the same time, she blamed Ruskin's own mutability: "Every day brings to my ears more of the untrue and altogether inexcusable things he has said of me ... "
It was extraordinary to read these intimate accounts of a long-dead love: their sepia words fell out of tiny envelopes bound in ancient ribbons; but their passion seemed as strong as the day they were written. Ruskin on one hand railed against Rose for her religious mania but, on the other, refused to accept the reality of their situation. It was difficult to know whom to blame: Rose for her adolescent intransigence, or Ruskin for his stubborn egotism; as a man who lived with and through art, he seemed unable to disentangle Rose from his aesthetic theories, even as she haunted his dreams. One afternoon in January 1870, he entered the Royal Academy to find Rose standing there. The chance encounter hit Ruskin like a physical blow. It was the first time he had seen her for four years. In his pocket, pressed between thin gold plates, he carried the letter in which she promised to consider their marriage; now he offered to return it. Rose declined. Ruskin was reduced to roaming the streets she had walked and running after carriages in which he thought he had seen her. And as Rose's illness turned worse, he announced to the world, in his monthly newsletter, Fors Clavigera - one of the more extraordinary publications of the Victorian era - that "the woman I hoped to be my wife is dying."
It was a drama played out to a pre-Raphaelite love of morbidity, a fatal conflation of innocence, sex and death. Ten years earlier, Dante Gabriel Rossetti's lover and muse, Lizzie Siddal - whom Ruskin regarded as a genius - had committed suicide, overdosing on the laudanum she took to assuage the symptoms of consumption (and, perhaps, her husband's infidelities). As Rossetti had her body exhumed to retrieve the poems he had placed in her coffin, he immortalised her as his Beata Beatrix. Through the painting's watery, crepuscular haze, Siddal emerges as a symbolist sybil, caught between sexuality and spirituality in an echo of the Swedenborgian notion that the union of a man and a woman on earth formed an angel in heaven; an aesthetic elsewhere embodied in the photographs of Julia Margaret Cameron, with their virginal children bedecked in goose-feather wings and seemingly suspended in amniotic fluid.
Now Ruskin - who had considered Rossetti to be his best friend - faced the loss of his own untarnished angel. Yet far from freeing him, Rose's death in a Dublin nursing home on May 25, 1875, merely tightened her grip on his psyche. Beset with grief, Ruskin retreated to Broadlands, the Hampshire home of the Cowpers, who had played go-betweens in the tortuous affair. William Cowper, illegitimate son of Lord Palmerston, and his wife, Georgiana (with whom Ruskin too had fallen in love many years before), enthusiastically embraced the tenets of the Victorian new age - phrenology, vegetarianism, anti-blood sports, homeopathy and, above all, spiritualism. Indeed, Rossetti had completed Beata Beatrix for them; the painting now hung at Broadlands as a psychic icon, witness to the weird circle that convened there.
Two years earlier, Ruskin had proposed to set up his utopian Guild of St George in the grounds of Broadlands, with Rose and himself living in the first of its cottages. Utopianism had been associated with spiritualism ever since Robert Owen's conversion to the new faith in the 1840s; now this Hampshire mansion, on the edge of the New Forest, was to be the site of a new experiment. Behind its shuttered windows, a bizarre coven of mediums assembled, led by Annie Andrews, a young woman who claimed she "often left her body to transverse the spheres" and saw "little wingless angels". On a dark December afternoon in 1875, she told Ruskin that Rose stood behind him, even as they spoke. It was a shattering revelation for the emotionally vulnerable critic: "And I'm as giddy as if I had been thrown off Strasburg steeple and stopped in the air."
How far Ruskin had been entrapped by conniving mediums remains unclear; but the effect was to subsume the memory of Rose into a kind of suicidal death-cult - and in the process plunge Ruskin into madness. In Venice that Christmas, 1876, he re-created Rose as St Ursula, the martyred British virgin he painted in his copy of Carpaccio's The Dream of St Ursula, an effigy of his obsession, a memento mori: "There she lies, so real that when the room's quiet - I get afraid of waking her!" In his deranged mind, Ursula and Rose had become interchangeable; and in an echo of Dante's Beatrice, he blasphemously imagined a physical reunion with his lover's spirit.
It now seems clear that Rose's death was subsumed into Ruskin's personal apocalypse. Her loss coincided with the plague cloud that threatened his Eden; an industrial penumbra drifting north from Manchester's cottonopolis and Bradford's satanic mills to Brantwood, his Cumbrian refuge perched over Coniston Water. There, in a specially constructed lantern-like oriel added to his bedroom, Ruskin looked across the lake, a Caspar David Friedrich figure both isolated from and a part of the land whose healing he sought. And there, in the summer of 1878, a new madness came upon him. He was convinced that Rose had come back as his bride, dressed in white, with Joan of Arc and William Cowper as attendants. He called out for his "Rose-Posie", crying, "Everything white! Everything black!", as if all England were caught up in his nightmare. Brantwood, his utopia, had now became his asylum.
Ruskin died on January 20 1900, never having fully regained his senses, yet he was able to dictate his defiant memoir, Praeterita , before words became truly useless: "Some wise, and prettily mannered people have told me I shouldn't say anything about Rosie at all. But I am too old now to take advice, and I won't have this following letter - the first she ever wrote me - moulder away." It was a heart-rending coda to the affair that had destroyed his life. The letter was pathetic, inconsequential, a child's report on a day out in Nice - "So you thought of us, dear St Crumpet, and we too thought so much of you" - but in its innocent prattle lay the source of Ruskin's pain, and all that followed from it.
· Philip Hoare's England's Lost Eden will be published by Fourth Estate on Februrary 28, priced £20.