Images

Images [εἴδωλα] were believed by Epicurus and his followers to somehow "flow" or emanate from material objects and, traveling through the air, strike our eyes; they were film-like and evanescent, and were subject to various distortions due to the consistency of the material through which they traveled: the classic examples of the tower that appears round from a distance and through the fog, yet is octagonal in reality, or of the oar that, half-submerged in the water, looks crooked, while it is perfectly straight in reality, demonstrate this phenomenon.

With the necessary refinement(s) of modern optical science, Epicurus' understanding is not too far-fetched; these refinements stem principally from the modern understanding that no film-like matter, but energy (i.e. light) is reflected upon illuminated objects, and thus their visual properties (e.g. shape, size, color, etc.) imprinted on the retina of the viewer's eyes.

Science aside, Epicurus applied his notion of images to numerous philosophical issues, such as the nature of dreams, the workings of memory, the nature of the gods, and many others.