THERE are, perhaps, two kinds of hoaxes. The first works only so long as it remains undiscovered. The second, by contrast, depends upon being discovered: only when the hoaxer's cover is blown will the point of the hoax be revealed. Most scientific hoaxes - or 'fraud', to use the stronger term - belong in the first category. Literary instances are rare and usually involve obscurer psychological impulses that stretch the limits of the term (Paul Radley, Demidenko/Darville). Examples ofthe second kind are 'core business' for the arts and humanities, from the Ern Malley affair to Sokal and Social Text. In these cases, the hoaxers might well blow their own cover, for that's the point: to make the hoax news. At its strongest, the hoax in this mode can be understood as a form of satire, exposing modishness, pretension, bias or sheer ignorance from the standpoint of some universal or more traditional system of values. The strategic fraud is perpetrated to expose a larger fraudulence.