a little eidola

from: http://www.iep.utm.edu/democrit/

Maintaining his atomic theory throughout, Democritus introduced the hypothesis of images or idols (eidola), a kind of emanation from external objects, which make an impression on our senses, and from the influence of which he deduced sensation (aesthesis) and thought (noesis). He distinguished between a rude, imperfect, and therefore false perception and a true one. In the same manner, consistent with this theory, he accounted for the popular notions of Deity; partly through our incapacity to understand fully the phenomena of which we are witnesses, and partly from the impressions communicated by certain beings (eidola) of enormous stature and resembling the human figure which inhabit the air. We know these from dreams and the causes of divination. He carried his theory into practical philosophy also, laying down that happiness consisted in an even temperament. From this he deduced his moral principles and prudential maxims. It was from Democritus that Epicurus borrowed the principal features of his philosophy.