"...Poetically Man Dwells..." § 223

What is God? Unknown, yet
Full of his qualities is the
Face of the sky. For the lightnings
Are the wrath of a god. The more something
Is invisible, the more it yields to what's alien.

What remains alien to the god, the sight of the sky—this is what is familiar to man. And what is that? Everything that shimmers and blooms in the sky and thus under the sky and thus on earth, everything that sounds and is fragrant, rises and comes—but also everything that goes and stumbles, moans and falls silent, pales and darkens. Into this, which is intimate to man but alien to the god, the unknown imparts himself, in order to remain guarded within it as the unknown. But the poet calls all the brightness of the sights of the sky and every sound of its courses and breezes into the singing word and there makes them shine and ring. Yet the poet, if he is a poet, does not describe the mere appearance of sky and earth. The poet calls, in the sights of the sky, that which in its very self-disclosure causes the appearance of that which conceals itself, and indeed as that which conceals itself. In the familiar appearances, the poet calls the alien as that to which the invisible imparts itself in order to remain what it is—unknown.

The poet makes poetry only when he takes the measure, by saying the sights of heaven in such a way that he submits to its appearances as to the alien element to which the unknown god has "yielded." Our current name for the sight and appearance of something is "image." The nature of the image is to let something be seen. By contrast, copies and imitations are already mere variations on the genuine image which, as a sight or spectacle, lets the invisible be seen and so imagines the invisible in something alien to it. Because poetry takes that mysterious measure, to wit, in the face of the sky, therefore it speaks in "images." This is why poetic images are imaginings in a distinctive sense: not mere fancies and illusions but imaginings that are visible inclusions of the alien in the sight of the familiar. The poetic saying of images gathers the brightness and sound of the heavenly appearances into one with the darkness and silence of what is alien.

Martin Heidegger (GA 7) Poetry, Language, Thought