The virus itself was ideally cast, a character of demonic ingenuity. We watched its unfolding biography in disbelief. As each new detail emerged - from its unpredictably long dormancy period to its ruthless employment of the body's own systems - the feeling has grown that a malign nature has consciously formed this demon specifically to expose our impotence. It was even possessed of a terrible historical accuracy, in that it attacked a newly sexually liberated generation in the midst of a period - the Eighties - of reckless affluence.
As a result, considered purely as an intellectual phenomenon, Aids has provided a playground of visions. It has lurked behind fictional metaphors, flaunted itself as political crusade, drawn down anathemas from the moralists and provided philosophers with endless material for global gloom or internecine dispute.
But Aids is changing. Its days of demonic stardom are numbered. Apocalyptic rhetoric is now scarce. The number of new cases in Britain seems - according to an imminent Public Health Laboratory Service report - to be reaching a plateau instead of pursuing an exponential increase. All the worst forecasts of the spread of Aids made in the mid-Eighties were, in the short term at least, wildly exaggerated. Even the appalling figures in Africa are being questioned.
Aids is in the process of becoming just one modern hazard among many, a great grief for some but a mere possibility for most. Unless, suddenly, the figures go haywire, Aids, at least in its incarnation as a modern Black Death, is about to become history.
But before the syndrome undergoes this transition, it is worth asking what Aids the idea was all about. How did it become such an evil augury for the entire world?
It was, first of all, about technological pessimism. Aids came from nowhere. It was a 'new' disease. But newness in such a context was itself a novelty. Penicillin, streptomycin, the Salk vaccine and the defeat of smallpox had convinced us that conquering disease was a steady war of attrition that we must inevitably win. We had thought we lived in a world in which the disease population was fixed. Any inroads into this population could thus be regarded as absolute progress. Of course, scientists knew of the possibility of new diseases, but Aids gave us all the bad news.
This shock was the precise correlative of the shock that launched modern environmentalism. When we realised that small doses of DDT accumulated to become large ones in the bodies of birds and animals, we also realised that a mechanically direct confrontation with nature was not the answer. With that shock in the Fifties and with Aids in the Eighties, it was realised that nature was too complex to be meddled with and too devious to be defeated.
This humiliation was accompanied by a terrible joy, a revelling in the dreadful implications. Technological Faust had been damned. Much of the eagerness with which the most apocalyptic Aids scenarios were embraced can be explained by man's need for justice, even when he is to be found guilty. We feel satisfied to be told that we have gone too far, because this at least means that there is a 'too far' to go. It is precisely like being told that there is a God.
So in 1986, the year of massive government anti-Aids campaigns, condoms being waved helpfully on television screens and the absolute necessity of discussing anal intercourse, sober commentators announced the end of the world as we knew it. Aids was, said Peter Jenkins, 'perhaps the greatest peacetime challenge to government in our lifetimes'. It was, said Jeremy Paxman, 'the greatest threat to public health since the bubonic plague' and, he added, 'the sexual counter-revolution may soon be upon us'. And, incredible though it seems now, the Sunday Times called for hundreds of millions of pounds to be diverted from other projects to fight the new Black Death.
There seemed to be solid authority for all this. Dr Charles Everett Koop, the US Surgeon-General, had forecast 100 million cases by the year 2000. This was, truly, a global cull, a millennial message to the planet.
The evocations of ancient scourges such as the plague - syphilis was also frequently mentioned - were an important ingredient in the joy. In modern comfort we had read of the terrors of the past, the intimate proximity of death, and thought we should never have to endure such horrors. But Aids said we would. You get it, you die. There are no consolations to be found in our medical paraphernalia, any more than there were to be found in the streets of London in 1665.
Plus, of course, you got it from sex. Paxman's 'counter-revolution' was expressed as metaphor. Sex killed you. Glenn Close played, in effect, the human immunodeficiency virus as woman scorned in Fatal Attraction, a movie that spawned a host of diseased-sex sagas. By 1988 the disease- sex link prompted a libertarian backlash. 'We are producing a generation of cripples who are scared of sex,' said one of the few remaining enthusiasts for 'healthy sex', that old Scandinavia of the British imagination.
The easiest, most seductive joy, however, was that of the moralist. Told you so, said Sir James Anderton, then Chief Constable of Manchester, who warned that 'people at risk are swirling around in a cesspit of their own making'. It was, in the event, irresistible. What else could this be but the judgement of God? But why did God have such a particular loathing for anal intercourse? Surely there were worse sins?
Against this was the attempt to turn Aids into a cause. This necessitated the insistence that it was not just a 'gay plague'. We were all at risk. Attempts to suggest this was a self-inflicted wound of the sexually specialised were part of a plot to cut Aids funding. In some bizarre way it was suggested that governments must 'do something'. What?
The mysterious origins of the virus were exploited by the conspiracy theorists. The most respectable origin theory - that the virus had leapt from monkeys in Africa - was said to be a cover; it was really a germ warfare bug, or a deliberate assault on homosexuals by fundamentalist Republicans. But the Aids crusade was, and remains, desperate and slightly pointless. Everything that could be done was being done. All Aids-as-a-cause could really do was peer-pressure the stars into wearing 'awareness' ribbons at the Oscars. Awareness of what? Death?
And, in spite of the awareness campaign, 'coming out' as an Aids victim remained a problem. It seemed that even the famous and supposedly unrepressed found it hard to admit to a condition that pointed overwhelmingly in the public mind to certain behaviour patterns. But, equally, 'coming out' was not just an admission but also a statement that you were doomed.
Susan Sontag attempted, uncharacteristically feebly, to disentangle all this by insisting in Aids and its Metaphors in 1988 that it was just a disease. All the judgements and the apocalypses did not alter the simple fact that this was just something nasty that happened to you, like cancer or a car crash. This was feeble, however, because she only really took on easy targets such as the fundamentalists who believed that Aids was the judgement of God. Furthermore, the whole point of Aids was that it showed nothing was 'just a disease' until the culture said it was. The 'metaphors' were as much part of the phenomenon as the virus.
Deeper, or perhaps just more excitable thinkers such as Jean Baudrillard identified Aids as the emblem of a deadly systems crisis of our own devising. 'Aids,' he has written, 'is the product of the murderous transparency of sex affecting entire human groups.' We build systems, of communication, of life, which become autonomous, creating other systems, new viral pathways of communication and correspondence. The final, terrible perfection of HIV was that it demonstrated how our happy, modern, global interconnectedness - an end to war, Michael Jackson and Coke for all - could rise up and destroy us.
This was the most potent and will be the most lasting aspect of the Aids idea. Even if the disease drifts into the background of our concerns, it will leave us with a new version of an old foreboding: the fear that we are 'wrong' in the world; strangers in a strange land; that, for all our competence, nature will always be able to outwit us. This is, of course, a religious insight in its insistence that, however far we go, we shall always be subject to a system greater than any we have devised.
All of which may be seen as a kind of spiritual luxury. For, if Aids is now slipping down our anxiety agenda and the rich continue to take the right precautions, then it will become a disease of the poor and of Africa, rather than of Rock Hudson and Freddie Mercury; and certainly no longer worth the drug companies' billions. It would be a 'problem', an area of concern, but no longer the Black Death. Such, in the modern West, is the history of ideas: rapid and fickle, even when toying with The End.