Since its invention, photography has been defined by its indexical capacity to document the visible world—what Barthes famously called its “that-has-been.” “The Unphotographable,” as Fraenkel Gallery titled its recent show, challenged this received truth, unearthing, according to curator and gallery owner Jeffrey Fraenkel, “a parallel history in which photographers and other artists have attempted to describe by photographic means that which is not so readily seen: thought, time, ghosts, god, dreams.” Spanning a broad historical and conceptual terrain—from nineteenth-century spiritualist