time. It looks for time in the Now that is flowing away, escaping. That something is past means: now it is no more; that something is in the future means: not yet.

The explicit question concerning the 'essence' of time ordinarily remains within the everyday experience of time. Time is the heavens or, rather, their revolving motion; time is movement.* It is clear from both statements that one looks for time in those things one refers to when one specifies the 'Then' of one's concerns on a daily basis: the heavens and the course of the sun. The first surviving treatise on time, whose findings have subsequently been, and still are, highly authoritative, namely Aristotle's discussion in his Physics (ontology of the world), also adheres to the most common way of encountering time.**

Aristotle calls to mind the state of affairs addressed in these statements and concludes: although time is not movement, it is nevertheless part and parcel of what is moved. What is time itself? The possibility [78] of highlighting the phenomenon of time and grasping it ontologically in light of this given state of affairs [vorgegebenen Tatbestand] requires us first to understand 'movement' ontologically. Aristotle discovered movement as an ontological characteristic of entities [des Seienden] and conceptualized it ontologically. Compared with Plato, he reached a more original ground within the same research project [Forschungstendenz]. For the first time, this opened up the possibility of delineating 'time' ontologically.(1)

The term 'movement' (κίνησις) encompasses all phenomena involving a change [Umschlagens] 'from-to' (μεταβολή); alteration (as in the process of dyeing something); increase and decrease; change of place. ἡ τοῦ δυνάμει ὄντος ἐντελέχεια ᾗ τοιοῦτον, κίνησίς ἐστιν. (2)*** Movement is ἐντελέχεια. This is an ontological characteristic of entities [Seiendem] and signifies: maintaining itself in a state of completing [Fertigsein], the state of being present-at-hand (presence) [Vorhandenheit (Anwesenheit)]. Movement is in fact the present-at-hand-ness of an entity

* See Aristotle, Physics, Δ 10, 218a 31-b8.

** Bergson's theory of time also clearly developed through an opposing take on Aristotle.

(1) is the specifically ontological concept of movement constitutively present in the Aristotelian definition of time?
see Physics Γ 2, 201 b31 Physics Θ 5, 257 b8

(2) κίνησις ἐντελέχεια κινητοῦ ἀτελής Compare Met. Θ

*** Physics Γ1. 201 a 10 sq.


The Concept of Time - 1924 article (GA 64) by Martin Heidegger