Timothy leary's dead ...

... long live Terence McKenna

He Is A cult hero at the exploratory end of the rave scene, he has been variously described as a "psychoactive visionary" and "altered Statesman", and he has appeared on techno recordings by, among others, the Shamen, writes Oliver Bennett.

Now this 50-year-old American, Terence McKenna, is a global presence. Since Timothy Leary dropped out for the last time earlier this year, McKenna has become the new eminence grise of the psychedelic intelligentsia, via the alternative lecture circuit, the Internet and a canon of books with titles such as True Hallucinations.

McKenna lives as a semi-recluse in the hills of Hawaii. A couple of years ago he was in London to lecture at Megatripolis nightclub: now he's back to take part in The Incident at the ICA in London (11-15 October), an exploration of aliens, astra travel and other strange phenomena. Here, he will attempt to explain his grand unifying theory, Time Wave Zero, nothing less than a parallel history of the world, with psychedelic drugs as the missing link, proposing that we once lived in primordial, stoned bliss. "The basic idea is that at a stage of human evolution, in came psilocybin, which made extraordinary cultural advances," he says.

Much of his flock is composed of ravers and new age trippers, who regard McKenna as an oracular figure. "Psychedelics, the new communications technology and the youth culture: these three things have some chance of defining some kind of truth that isn't a mercantile techno-Fascism," he asserts.

An apocalyptic edge to his work has endeared him to folk millenarians, for part of Time Wave Zero proposes that the world (as we know it) is due to end on 21 December, 2012: the date that Mayan astronomers thought to be the end of time. "One distillation of my schtick might lead you to the end of the world," he says; or at least to the start of something else. Get picking, or get packing.