“Even someone who is not an actor acts while on set, though he is playing himself,” Eisner says in an interview. “A Quiet Monastery” is such a documentary performance. The performer is Bardiashvili, a watchman who looks into the camera with a gap-toothed smile and issues one piece of “everyday wisdom” after another. His stage is the construction site he guards and his native town, both resembling a post-apocalyptic landscape.