The jacket photograph is of Kingscote Garden, on the campus of Stanford University. It is little known and the author explains that, not being a gardener, he went there "on several occasions" to "gain clarity about what a garden is in essence". Oh heck, I mused, is this the equivalent of a sex manual by a Catholic priest? Learning that Robert Pogue Harrison is Rosina Pierotti professor of Italian literature at Stanford supported my hypothesis. But I was wrong.

The book is about gardens as a metaphor for the human condition. It is not about the history of designed gardens or of gardening as a practice. Harrison draws freely and with brilliance from 5,000 years of western literature and criticism, including works on philosophy and garden history. His essay on Plato's Academy Garden, which follows the essay on Kingscote, is the nearest I have come to a page-turner in the literature of gardens. It links the modern experience of teaching, which I and many Times ÖйúAƬ readers share with Harrison, to the histories of western academia and western gardens.

The essay begins with a reflection on graduation day at Stanford. Harrison observes "the throng of parents who descend on the campus during those scintillating days in June". As they view the historic quadrangle and wander "the grounds of a beautifully kept garden complex, with its expansive lawns, fountains, groves, courtyards, and sports fields ... you can see in the parents' faces the spell of enchantment".

But, he asks, "what does education have to do with gardens?", before explaining that the association extends back, through quadrangles and cloisters, to Roman villas and Plato's grove, which was dedicated to the god Academos. The Phaedrus, in a famous passage, disparages writing for being at one remove from truth (logos). Like painting, writing is but a shadow. Genuine teaching is more like planting than inscribing. "This ability to discriminate between worthy and unworthy interlocutors is critical to the educator, as well as to the student, as the gardening analogy that Socrates now puts forth makes clear."

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In the age of Wikipedia, when "facts" of ever-varied quality are widely available, the necessity for discrimination may give us teachers continued employment. Harrison states that for Plato, "the 'highest happiness' a human being can attain ... comes from nourishing new life in the soul of a student ... The teacher plants seeds in a student's soul which in turn will produce new seeds to be planted in other students' souls."

Many teachers, I hope, will have experienced the "highest happiness". For Harrison, the discussion of Plato is an incident on an unfurling canvas which, in 15 essays, includes discussion of the Epic of Gilgamesh, the Garden of Eden, Boccaccio, monastery gardens, Dante's paradise, Versailles, Voltaire and the treatment of paradise in the Bible and the Koran. His view of the human condition, explained in the preface, is that "where history unleashes its destructive and annihilating forces, we must, if we are to preserve our sanity, to say nothing of our humanity, work against and in spite of them. We must seek out healing or redemptive forces and allow them to grow in us. That is what it means to tend our garden. The pronominal adjective used by Voltaire - notre - points to the world we share in common." We can never rest; we must always work; we are driven to endless acquisition; such is the human condition.

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It is a grand and fascinating theme, which led me to two reflections on the narrower field of garden history. The first is that studying the composition of paving, planting, water, landform and structures distracts garden historians from the world of ideas, which is the key factor in all garden design. Although I have spent half a lifetime reading about this aspect of gardens, Harrison's excellent bibliographic notes left me wondering if I should have spent the other half of my life, or whatever now remains, on the literature he analyses with such skill - and with which I am comparatively unacquainted.

My other reflection is that John Dixon Hunt, professor of the history and theory of landscape at the University of Pennsylvania, is right to treat garden history as a "word and image" subject. One needs to balance an examination of what was done with consideration of the ideas and motives that underlie design approaches. And one needs to remember the differences between garden types: sanctuaries, gymnasia, academic groves, palace gardens, hunting parks, domestic courts and horticultural plots are separate entities, as are churches, forts and dwellings in architectural history. Medieval cathedrals symbolise piety but this is not true of all medieval buildings. Nor can one generalise about "gardens". The aristocrats of Voltaire's day - in contrast to many wealthy gardeners in our own time - were not attracted by the practicalities of gardening. When concluding Candide with the declaration "Il faut cultiver notre jardin", Voltaire can hardly have meant that we should clip our parterres. He was surely thinking, like Horace, of fruit, vegetables and honey.

Harrison tends to conflate garden types and this is a weakness in his argument. Plato's Academy is described as "much like the immured hunting preserves of the Persian kings, from which comes the word paradise". His etymology is accurate but a pairidaeza was different in kind from an academy. It was a place for action, not for rest and reflection, and the pairidaeza is unlikely to have been cultivated. It seems to have been a place for wild and exotic beasts.

My guess is that Plato's Academy owed more to Egypt than to Persia and that its educational use was related to that of temple sanctuaries on the fringes of the Western Desert, which also had sacred groves. Plato's Academy was a place for the intellectual descendants of Egyptian priests to gather and talk and learn. Unusually for the ancient world, the Egyptians did not make hunting parks. They hunted in the desert or on the Nile instead.

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Harrison is a careful as well as an inspiring scholar and, notwithstanding his interest in paradise gardens, he narrowly evades the traditional garden historian's error of stating that all Islamic gardens are symbols of paradise. His aim is to compare and contrast the Christian and Islamic visions of paradise. In the Bible, the Garden of Eden is "a kind of half-way place between hell and heaven" from which Adam was sent forth to till the ground whence he was taken. In contrast, "Islam boldly identifies paradise with the Garden of Eden".

The paradise of Islam is richly detailed and "seems to represent a particular male fantasy of satisfied appetites". Harrison remarks that it is unclear whether comparable pleasures are on offer to female aspirants and "what sorts of rewards await them". Given the luscious accounts of dark-eyed houris and high-breasted maidens reclining on jewelled couches, the omission of comparable feminine fantasies was perhaps a tasteful editorial decision by those who inscribed the truths revealed unto Muhammad. But women would surely enjoy being "lodged in peace together amidst gardens and fountains, arrayed in rich silks and fine brocade" (Koran 44:45-47), as they enjoy earthly gardens.

THE AUTHOR

Although Robert Pogue Harrison's specialist subject is Italian literature, he has written on a variety of subjects, including the multiple ways in which the Western imagination has symbolised and represented forests, and the relations the living maintain with the dead in diverse secular realms.

He believes that the academy should be more open, saying that "so much of what we do in academia is a world unto itself". To that end, he presents a radio show called Entitled Opinions, where each week he invites a scholar to discuss his or her research interests.

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Pogue Harrison was born in Izmir, Turkey, and educated in Italy and the US. He received his doctorate in romance studies from Cornell University in 1984, with a dissertation on Dante's Vita Nuova.

In 1985 he accepted a visiting assistant professorship in the department of French and Italian at Stanford. He was promoted to full professor in 1995. In 1997 Stanford offered him the Rosina Pierotti chair. In 2002, he was named chair of the department of French and Italian, a position that he still holds.

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- Sarah Cunnane