If being (Sein) reveals its truth by way of aletheia or disclosure of phenomena, i.e., the visible world, then the light that makes the being of beings (Seiende) accessible to human perception also needs the contrast of its opposite: the lethe or hiddenness of darkness. The light and the dark both make up the measure of being: a notion that was once best understood by the ancient Greeks, who for them even the gods existed within this measure (metra), and like the mortals, fate was allotted to them.