any given time." Ὁ ἀεὶ βασιλεύων = the one who is ruler at the timenot the "eternal" ruler. With the word ἀεί what one has in view is the notion of "staying for a while," specifically in the sense of presencing. The ἀίδιον is something present of and by itself without other assistance, and for this reason perhaps something constantly present. Here we are thinking not with regard to "duration" but with regard to presencing. This is the clue for correctly interpreting the opposing concept, γινόμενον ἀρειράκις. In Greek thought, what comes to be and passes away is what is sometimes present, sometimes absent — without limit. But πέρας in Greek philosophy is not "limit" in the sense of the outer boundary, the point where something ends. The limit is always what limits, defines, gives footing and stability, that by which and in which something begins and is. Whatever becomes present and absent without limit has of and by itself no presencing, and it devolves into instability. The distinction between beings proper and non-beings does not consist in the fact that beings proper perdure without restriction whereas non-beings always have their duration broken off. With regard to duration both could be either restricted or unrestricted. The decisive factor is rather that beings proper are present of and by themselves and for this reason are encountered as what is always already present — ὑποκείμενον πρῶτον. Non-beings, on the other hand, are sometimes present, sometimes absent, because they are present only on the basis of something already present; that is, along with it they make their appearance or [340] remain absent. Beings (in the sense of the "elemental") are "always 'there,'" non-beings are "always gone" — where "there" and "gone" are understood on the basis of presencing and not with regard to mere "duration." The later distinction between aeternitas and sempiternitas would come closest to the Greek distinction we have just clarified. Aeternitas is the nunc stans, sempiternitas is the nunc fluens. But even here the original essence of being, as the Greeks experienced it, has already vanished. The distinction refers not to the mode of mere duration but only to that of change. What "stays" is the unchanging, what flows is the "fleeting," the changing. But both are equally understood in terms of something continuing without interruption.

For the Greeks, however, "being" means: presencing into the unbidden. What is decisive is not the duration and extent of the presencing but rather whether the presencing is dispensed into the unhidden and simple, and thus withdrawn into the hidden and inexhausted, or whether presencing is distorted (ψεῦδος) into a mere "looks like," into "mere appearance," instead of being maintained in undistortedness (ἀ-τρέκεια ). Only by seeing the opposition of unhiddenness and seeming can we adequately know what the essence of οὐσία is for the Greeks. Such knowledge is the condition for


Martin Heidegger (GA 9) On the Essence and Concept of Φύσις in Aristotle's Physics B, I - Pathmarks