Aristotle’s derivation of the concept of time from empirical observation – of changes occurring in our minds, of the movement of objects in space – is obvious. Concerning the former he says in the Physics that ‘when we do not change the state of our minds at all (hotan mêden autoi metaballȏmen tên dianoian), or do not notice our changing (ê lathȏmen metaballontes), it does not seem to us that time has occurred (ou dokei hêmin gegonenai chronos, 218b22-24)… for we perceive movement and time together (hama gar kinêseȏs aisthanometha kai chronou): for even when it were dark (kai gar ean êi skotos) and we were not being affected through the body at all (kai mêden dia tou sȏmatos paschȏmen), if any movement took place in the mind (kinêsis de tis en têi psuchêi enêi), it seems to us at once that also some time has occurred (euthus hama dokei tis gegonenai kai chronos, 219a3-6).’ Concerning the latter he says: ‘Since what is moved is moved from something to something (epei de to kinoumenon kineitai ek tinos eis ti), and all magnitude is continuous (kai pan megethos suneches), the movement follows the magnitude (akolouthei tȏi megethei hê kinêsis); because the magnitude is continuous (dia gar to to megethos einai suneches), the movement too is continuous (kai hê kinêsis estin suneches), and because of the movement the time is continuous (dia de tên kinêsin ho chronos); for the amount of time that has passed always appears to be the same as the amount of the movement that has taken place (hosê gar hê kinêsis, tosoutos kai ho chronos aiei dokei gegonenai).’ (219a10-14)
Viewed in terms of Locke’s two empirical sources of all our ideas, sensation (employed about external sensible objects) and reflection (employed about the internal operations of our minds), Aristotle’s concept of time is derived from both these sources. The external sensible object from which Aristotle derives his concept of time is phora, locomotion, movement of objects in topos, place/space. Locke’s internal operations of our minds correspond to Aristotle’s metabolê, i.e. change that affects our mind (tên dianoian).
Aristotle’s derivation of the concept of time both from sensation and reflection leads to his rejection of purely subjective concept of time. Thus in the Physics he considers the question, ‘which someone might ask (aporêseien an tis), whether if soul did not exist (poteron de mê ousês psuchês) time would exist or not (eiê an ho chronos ê ou, 223a21-22) … for if nothing but soul and intellect in soul can count (ei de mêden allo pephuken arithmein ê psuchê kai psuchês nous), there can be no time without soul (adunaton einai chronon psuchês mê ousês, 223a25-26)’. He solves the problem by saying that ‘time would be what it is (touto ho pote on estin ho chronos), if movement can exist without soul (ei endechetai kinêsin einai aneu psuchês); and the ‘before and after’ are in movement (to de proteron kai husteron en kinêsei estin), and time is these in so far as they are countable (chronos de taut’ estin hêi arithmêta estin, 223a27-29).
In contrast to Aristotle, Locke insists that we derive the idea of duration from reflection, not from sensation: ‘Men derive their ideas of duration [and thus of time, which Locke views as a simple mode of duration, J. T.] from their reflection on the train of the ideas they observe to succeed one another in their own understandings’ (An Essay Concerning Human Understanding, Bk. II, Ch. XIV, par. 4). ‘Thus by reflecting on the appearing of various ideas one after another in our understandings, we get the notion of succession; which if anyone should think we did rather get from our observation of motion by our senses, he will perhaps be of my mind when he considers that even motion produces in his mind an idea of succession no otherwise than as it produces there a continued train of distinguishable ideas’ (Ch. XIV, par. 6).
Historically, Lock’s insistence that we derive our concept of time from reflection, that even ‘our observation of motion by our senses’ produces in our minds the idea of succession and thus of time ‘no otherwise than as it produces there a continued train of distinguishable ideas’, appears to be pointing towards Kant, who views time as ‘the subjective condition (die subjektive Bedingung) under which all our intuitions take place’ (unter der alle Anschuungen in uns stattfinden können, B49, A33): ‘for all representations (weil alle Vorstellungen), whether they have or have not external things for their objects (sie mögen nun äussere Dinge zum Gegenstande haben, oder nicht), still in themselves (doch an sich selbst), as determinations of the mind (als Bestimmungen des Gemüts), belong to our internal state (zum inneren Zustande gehören); and because this internal state is subject to the formal condition of the internal intuition, that is, to time (dieser innere Zustand aber, unter der formalen Bedingung der inneren Anschauung, mithin der Zeit gehört) – time is (so ist die Zeit) a condition a priori of all phenomena whatsoever (eine Bedingung a priori von aller Erscheinungen überhaupt) – the immediate condition of all internal (und zwar die unmittelbare Bedingung der inneren), and thereby the mediate condition of all external phenomena (und eben dadurch mittelbar auch der äusseren Erscheinungen).’ (B50, A34, tr. Meiklejohn)
But from Kant’s point of view his own conception of time has as little in common with Locke’s derivation of the concept of time from reflection as with Aristotle’s derivation of time from changes in our minds and from locomotion. In Kant’s view, time is an a priori intuition, which makes all reflection and sensation possible. In his view, all changes of mind and observations of locomotion, from which Aristotle derives time, and all reflections of the succession of ideas, from which Locke derives time, can be taken away, but time itself cannot be taken away. To put it in Kant’s own words: ‘Time is a necessary representation (Die Zeit ist eine notwendige Vorstellung,), lying at the foundation of all our intuitions (die allen Anschauungen zum Grunde liegt.). With regard to phenomena in general, we cannot think away time from them, and represent them to ourselves as out of and unconnected with time (Man kann in Ansehung der Erscheinungen überhaupt die Zeit selbst nicht aufheben,), but we can quite well represent to ourselves time void of phenomena (ob man zwar ganz wohl die Erscheinungen aus der Zeit wegnehmen kann.). Time is therefore given a priori (Die Zeit ist also a priori gegeben.). In it alone is all reality of phenomena possible (In ihr allein ist alle Wirklichkeit der Erscheinungen möglich.). These may be annihilated in thought (Diese können insgesamt wegfallen,), but time itself, as the universal condition of their possibility (aber sie selbst als die allgemeine Bedingung ihrer Möglichkeit,), cannot be annulled (kann nicht aufgehoben werden.).’ (B46, A31, tr. Meiklejohn)
Kant’s ‘intuition’ (Anschaung) of time is subjective in relation to ‘thing in itself’; he regards ‘time as merely the subjective condition (die Zeit nichts als die subjektive Bedingung ist,) under which all our intuitions take place (unter der alle Anschauungen in uns stattfinden können) (B49, A33) … If we abstract our internal intuition of ourselves and all external intuitions , possible only by virtue of this internal intuition and presented to us by our faculty of representation (Wenn wir von unserer Art, uns selbst innerlich anzuschauen, und vermittelst dieser Anschauung auch alle äusseren Anschauungen in der Vorstellungskraft zu befassen, abstrahieren,), and consequently take objects as they are in themselves (und mithin die Gegenstände nehmen, so wie sie an sich selbst sein mögen,), then time is nothing (so ist die Zeit nichts.).’ (B51, A34, tr. Meiklejohn)
But Kant’s ‘intuition’ (Anschauung) of time is objective in relation to all things we can ever encounter in our experience: ‘Nevertheless, in respect of all phenomena, consequently of all things which come within the sphere of our experience, it [i.e. time] is necessarily objective (Nichtsdestoweniger ist sie [i.e. die Zeit] in Ansehung aller Erscheinungen, mithin auch aller Dinge, die uns in der Erfahrung vorkommen können, notwendigerweise objektiv.).’ (B51, A35, tr. Meiklejohn) This is why he can maintain: ‘Thus our conception of time explains the possibility of so much synthetical knowledge a priori (Also erklärt unser Zeitbegriff die Möglichkeit so vieler synthetischer Erkenntnis a priori,), as is exhibited in the general doctrine of motion, which is not a little fruitful (als die allgemeine Bewegungslehre, die nicht wenig fruchtbar ist, darlegt.).’ (B49, A32, tr. Meiklejohn)