In the late 1970s and early 1980s philosophers and social historians examining the connections between perception theory and photographic representation began to suspect the complicated role of photography as a cultural phenomenon. The relationship between documentary and expressive photography raised numerous questions: Why do two categories exist, especially when so many photographic artists use conventions invented and elaborated by non-artist documentarians? Is the distinction driven by the marketplace, or by scholarship in need of pigeonholes? Should art always resemble traditional forms--landscape, portrait, still life, formal or conceptual abstraction--and evidence always be distinguished by its subject? Why do historic documentary photographers increasingly enter the canon of fine art?