THE Roman poet-philosopher Lucretius, in De Rerum Natura, offers one of the earliest — and strangest — accounts of perception. Everything, he insists, is made of atoms and void, including appearances themselves. Objects are constantly shedding wafer-thin films of matter — simulacra — that drift through the air and strike our eyes. To see, then, is not merely to look, but to be struck: vision as contact, not contemplation. Mirrors bounce these films back at us; dreams recombine them into improbable pageants. Reality, for Lucretius, is already a kind of theatre.