many forms of motion or change as there are forms of being (201a8–9; ὥστε κινήσεως καὶ μεταβολῆς ἔστιν εἴδη τοσαῦτα ὅσα τοῦ ὄντος). This is why all change has the structure of “from something toward something” (ἐκ τινος εἰς τι). The moment of retaining the “from what” in anticipating the “to-ward what” that essentially characterizes motion is grounded in megethos, “magnitude” or “extension,” which Heidegger expresses with the German word “Dehnung.” Thus we read at Physics Δ.11 219a11–12 that “motion fol-lows magnitude” (ἀκολουθεῖ τῷ μεγέθει ἡ κίνησις). The crucial point is that the possibility of this magnitude and of the motion that follows it lies in the double structure of the categories themselves. Heidegger speaks here of a peculiar “relation of tension” (Spannungsverhältnis) in the categories (GA83, 233). We are also reminded that what we have here is the pros ti rela-tion we have seen to characterize motion; so now we see that motion has this structure because being in the sense of the categories has this structure. But there is something strange here, as Heidegger notes: the pros ti relation is itself one of the categories (see Categories, 1b26). “Therefore strange: a specific category is needed to clarify the structure of the other categories” (WP3, 3; cf. GA18, 324, 389–390).
This inner structure is itself grounded in the split that cuts across all categories and that Aristotle refers to at 201a9–10 between dunamis and entelecheia. The contradictory opposition between not being a table and being a table is a split between not-yet-being-a-table, that is, potentially being a table, and actually being a table; the “stretch,” “span,” or “tension” be-tween contraries that exists in the other categories is also grounded on the split between dunamis and entelecheia, for example, from being potentially white to being actually white and spanning all the gradations between. In the published protocol the importance of this close relation between being in the sense of the categories and being in the sense of dunamis and entelecheia, a relation in which the latter grounds the inner structure of the former, is given special emphasis, with Heidegger observing that “this is all the more important, given that Aristotle himself, while frequently enumerating the different regions of being, never in the writings that have been handed down to us discusses thematically the inner relation between the four horizons of being” (GA83, 234).
This is why motion, as existing in each of the categories, can be explained in its being only in terms of dunamis and energeia. Such an explanation is precisely what Aristotle offers when he defines motion as “the entelecheia of what exists in dunamis insofar as it is such” (201a10–11; ἡ τοῦ δυνάμει ὄντος