Robert Mapplethorpe shot Polaroids for only a few years, at the start of his career. These little objects—four by five inches at the largest, each an original—are the warmest and hottest things he ever made. In this one, the subject is unknown; it may be the artist himself. The position is both sacred and profane, a perfect Janus pose. He's preparing for prayer and sex. His hips rise around the implication of an invisible but completely open core. Everything we could ever know about a life lived in photographs, and everything we can never know, is all right here.