Never afraid to stick his ears above the parapet, Prince Charles has produced a book he proudly describes as "a call to revolution". Throwing moderation to the winds, he comes out in favour of happiness, sustainable development and cities fit to live in, while opposing greed, ugliness and environmental catastrophe. Has his old man got wind of this subversive stuff? Has the prince taken to selling Socialist Worker to the toilers of Clarence House?

Harmony is a hard book to summarise, since apart from Jedward and Marxist literary theory there is very little in what Charles describes as "being aware and alive in this extraordinary universe" that it leaves out. The unifying thread, however, is the need to abandon a soulless modernity for a traditional spirituality.

The book ranges from the mating habits of the albatross to the Sufi brotherhood, from carpet-weaving in Afghanistan to the mysterious five-pointed star you get when you superimpose the Earth's orbit on Mercury's. There is a quotation from the Emerald Tablet of Hermes ("that which is above is as that which is below, and that which is below is as that which is above"), which might just be a coded offer to swap Highgrove with a council house tenant. We move from reflections on the "grammar and geometry" of nature to the "magical mountain kingdom of Bhutan", where, as the book fails to point out, democracy is only recently known. There is some grudging admiration for the Large Hadron Collider ("will it enable us to re-find our place in nature? "), along with some unqualified approval of termites, Thomas Aquinas and the garden the prince has created at Highgrove "planted with fig, pomegranate and olive trees because they are mentioned in the Qur'an". This, one takes it, is his contribution to the war on terror.

There are, to be sure, limits to Charles's revolutionism. He wants the kind of change radical enough to do away with polluters and modernist architects, but not radical enough to do away with himself. Meanwhile, he is eager to share his thoughts with us on Francis Bacon's Novum Organum, Ficino's tome on Platonic theology, Marinetti's Futurist manifesto and a number of other texts he has almost certainly not read. He also offers us some incisive insights into figures such as Justus von Liebig, David Bohm and Karlheinz Stockhausen, whom he has very probably not heard of.

This is because, being a royal, he can employ people to do his reading for him. Two such loyal readers-cum-scribes, Tony Juniper and Ian Skelly, presumably wrote the hard bits of this book, such as how many power stations there are in the world, while the prince mixed in a number of high-minded platitudes reminiscent of a Get Well Soon card.

Like many a coffee-table creation, one of the volume's most alluring aspects is its smell. But there are also some rather fetching pictures of the Egyptian goddess Ma'at, the prince sitting on his sofa gazing benignly at a frog and various astrological diagrams of the cosmos. In somewhat more dubious taste is a photograph of the twin towers of Chartres cathedral, which are said to "resemble Christ's two fingers held aloft".

Discovering the same organic patterns everywhere you look is a familiar symptom of paranoia. In the prince's case, however, it represents an insight into the fundamental rhythms of the universe. If you press your face on a large piece of paper on a wall, he tells us, and let your arms describe natural arcs with a couple of pencils, you would find yourself creating certain cosmically symbolic circles. He forgets to add that you would also look a complete prat. Charles, to be sure, has the leisure for such communings, as others may not.

The point of having an enormous amount of money is not to have to think about the stuff and thus to be free to turn one's thoughts to more spiritual matters, like the mystical proportions of the Golden Ratio and why everyone in the depths of a recession keeps banging on unpoetically about growth and unemployment. The prince is darkly suspicious of economic growth – which is to say of other people's hunger for possessions rather than his own.

Old-style Tories like the prince support a system that breeds materialism and cultural cretinism, then throw up their hands in well-bred horror at what they have helped to bring into existence. Despite almost certainly never having heard of him – a deficiency that doesn't hold him back here – His Royal Highness should recall Bertolt Brecht's parable about the troubled king of the east who summoned his wise men and commanded them to inquire into the source of all the miseries in the world. The wise men duly investigated, and returned to the king with the answer that the source of the miseries was him.

Terry Eagleton's On Evil is published by Yale.