Appearing in the second sense simply gives space an outline and measures the space that has been opened up.92
But does not Parmenides’s saying already say that Being and apprehending, that is, what is viewed and seeing, belong together? Something viewed certainly belongs to seeing, but it does not follow that having been viewed as such and alone should and can determine the coming to presence of what is viewed. Parmenides’s saying precisely does not say that Being should be conceived on the basis of apprehending, that is, as something merely apprehended, but that apprehending is for the sake of Being. Apprehending should open up beings in such a way that it sets beings back into their Being, so that apprehending takes beings with regard to the fact that they set themselves forth and as what. But in the interpretation of Being as ἰδέα, not only is an essential consequence falsified into the essence itself, but this falsification is misinterpreted yet again—and this, too, happens in the course of Greek experience and interpretation.
The idea, as the look of that which is, constitutes what it is. The what-Being, the “essence” in this sense, that is, the concept of essence, in turn becomes ambiguous:
a. A being essentially unfolds,93 it holds sway, it summons and brings about what belongs to it, including conflict in particular.
b. A being essentially unfolds as this or that; it has this what-determination.
We have indicated—though here we cannot pursue the issue further—the way in which, when φύσις changes into ἰδέα, the τί ἔστιν (what-Being) comes forth and the ὅτι ἔστιν (that-Being) distinguishes itself in contrast to it; this is the essential provenance of the distinction between essentia and existentia.
92. Heidegger is contrasting the verb aufreißen (to rip open) with the related noun Aufriß (an outline, diagram, architectural projection, or perspective view).
93. See wesen in German-English Glossary.