Green looks at three distinct types of collaboration: the highly bureaucratic identities created by Joseph Kosuth, Ian Burn, Mel Ramsden, and other members of Art & Language in the late 1960s; the close-knit relationships based on marriage or lifetime partnership as practiced by the Boyle Family, Anne and Patrick Poirier, Helen Mayer Harrison and Newton Harrison; and couples -- like Christo and Jeanne-Claude, Gilbert & George, or Marina Abramovic and Ulay -- who developed third identities, effacing the individual artists almost entirely. These collaborations, Green contends, resulted in new and, at times, extreme authorial models that continue to inform current thinking about artistic identity and to illuminate the origins of postmodern art, suggesting, in the process, a new genealogy for art in the twenty-first century.