This essay argues that Don DeLillo's 2003 novel Cosmopolis presents a critique of the world of cyber capital that invokes and is framed by the long-standing Euro-American republican contrast of virtue and corruption. As always in such discourse, corruption endangers the republic, but in the increasingly mediated reality of the kosmou polites, the traditional counterweight of virtue is left with no ground on which to stand. DeLillo's book thereby takes a political turn, evoking, in the manner of the Menippean satire, a fantastical, dream-like vision of both individual and political illness.