Let us think back to Homer, who likewise already, almost reflexively, brings the presencing of a what-is-present into relation with light. We may recall a scene during the homecoming of Odysseus. With the departure of Eumaeus, Athena appears in the form of a beautiful young woman. The goddess appears to Odysseus. But his son Telemachus does not see her, and the poet says: οὐ γἀρ πως πάντεσσι θεοὶ φαίνονται ἐναργείς (Odyssey XVI, 161). “For the gods do not appear to everyone ἐναργείς”—this word is translated as “visible.” Yet ἀργὀς means gleaming. What gleams, shines forth from itself. What shines forth thus, presences forth from itself. Odysseus and Telemachus see the same woman. But Odysseus perceives the presencing of the goddess. Later, the Romans translated ἐνάργεια, the shining-forth-from-itself, with evidentia; evideri means to become visible. Evidence is thought in terms of the human being as the one who sees. In contrast, ἐνάργεια is a feature of presencing things themselves.-- On the Question Concerning the Determination of the Matter for Thinking
According to Plato, things owe their shining to a light. This relation of the ideas to light is understood as a metaphor. Nevertheless, the question remains to be asked: What is it about the proper nature of presencing that its determination requires and allows a transference to light? For long enough, thinkers have troubled over in what way determinations such as identity, otherness, sameness, movement, which belong to the presencing of what-is-present, can still be thought of as ideas. Is here concealed a completely different issue that becomes entirely inaccessible because of the modern reinterpretation of ἰδέα, namely, from the outward appearance of what-is-present to perceptio, to a constituted representation by the human I? The presence of what-is-present has as such no relation to light in the sense of brightness. But presence is referred to light in the sense of the clearing.