One consequence of being editor of the BMJ is that you are regularly sent papers describing a cure for AIDS and the cause of all cancers. Often these papers are written entirely in capital letters and copied to the Pope and Boris Yeltsin. Usually they can be rejected quickly, but sometimes you are left wondering if there might be something in the paper that is important. Medical science has a poor record of distinguishing geniuses from the deluded. This week the BMJ invites readers to make up their own minds on a hypothesis that has generated great controversy.

Peter Duesberg has argued that HIV is neither necessary nor …