"Beauty and horror in contemporary art" is the subtitle of the Royal Academy's "Apocalypse" exhibition. It's not a bad line. The fission of the beautiful and the horrific is precisely what produces the raw power of the apocalyptic genre. We forget, in our post- modern toying with the most barbaric images in the Book of Revelation - horned beasts, spectral horsemen, fire and sulphur, the armies of Armageddon - that it contains the most bewitchingly lovely depiction of paradise in the Bible:
Then I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea. And I John saw the holy city, new Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband. And I heard a great voice out of heaven saying, "Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people [ . . . ] And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any pain: for the former things are passed away." (Rev 21:1-4)
Although this passage follows swiftly the final defeat of Satan, it is not really postapocalyptic. On the contrary, it is the essence of apocalypse. The Greek word "apokalupsis" refers to an unveiling, and this is what is unveiled; without it, the blood-drenched drama of the previous 20 chapters would be meaningless. With it, however, something very strange is accomplished: the most terrible acts of violence, whether directed by or at the forces of good, are retrospectively sanctified. The world has ended for a purpose.
This is what makes apocalypse proper - the religious vision, extending over millennia from the Book of Daniel to the last poisoned supper of Heaven's Gate - so much more interesting and morally complex than secular caricatures of Armageddon. The beauty of violence is one of the greatest and most enduring of anthropological idees fixes, and in apocalypse it finds its most refined expression. The waves of catastrophe that come crashing down on humanity in Revelation have a grandeur to them that is derived from their divine origin. This presents the modern observer, who has been taught that empathy is crucial to understanding, with an almost impossible dilemma. If the peculiar symmetry of apocalypticism demands that the reward of the elect is balanced by the suffering of millions of the unsaved, does that make it intrinsically repugnant? How do we assess the motives of those who retreat into apocalypse? Are they mentally ill, or sane people labouring under a socially constructed delusion, or a mixture of the two?
I believe that this phenomenological tightrope has been walked most successfully by the historian Norman Cohn, whose classic study of medieval apocalyptic fanatics, The Pursuit of the Millennium, shows how the Last Judgement of orthodox Christianity mutated into homicidal visions of the End in the imaginations of people disorientated by social change. Controversially, Cohn applies his theory to the totalitarian excesses of the 20th century, suggesting that only millenarian patterns of belief can explain why apparently rational men could shovel babies into gas ovens or shoot millions of peasants: they thought they were carrying out the preordained plan of the Almighty, lightly secularised as "historical destiny". I think he is right. Far from excusing the actions of Hitler or Stalin, Cohn opens up a new dimension of their wickedness. It would be going too far to say that such evil originates in the structures of apocalypticism, which - despite everything - is often morally neutral. But now we know where the Nazis got their inspiration.
You could work some of this out, I reckon, simply by looking at the most memorable contribution to the Academy's exhibition, the Chapman brothers' 5,000-piece Hell. Here, the Nazis appear, perhaps for the first time in art, in their natural apocalyptic habitat: spewed out by a volcano, writhing in pits, rising from graves, tortured by many-headed mutants. Comparisons with Hieronymus Bosch miss the point - we must look further back. Ultimately, it is the scale of the work that impresses, rather than the nauseating detail: the multiplication of the horror possesses its own beauty, just as in the Book of Revelation.
What a terrific centrepiece Hell would have made to an intelligent exploration of millenarian tradition, taking in medieval evocations of the Last Judgement, the prophetic art of William Blake, Stanley Spencer's The Resurrection, Cookham. What we have instead is a lazy exploitation of the rapidly evaporating shock value of the word "apocalypse" devised by people who, as far as I can tell, have no other interest in the concept. The Chapmans' masterpiece apart, the only convincingly apocalyptic note was provided by the computer malfunctions that forced the temporary closure of three exhibits on the day I visited.
Could it have been the millennium bug?
"Apocalypse: beauty and horror in contemporary art" is at the Royal Academy, Piccadilly, London W1 (020 7300 8000) until 15 December
Damian Thompson's The End of Time is available in paperback from Vintage (£6.99)