“Should we understand a photographic document as being first and foremost an artifact of memory, a light-written ghost? Or is it more important to stress its status as a material thing created from pigment, silver, emulsion, paper, plastic, glass, silicon sensors, pulses of electricity? Or is the photograph primarily an opportunity to take or make, an arena for a special type of action?” On Polaroids, instantaneous photography, and memory over at The Nation.