Time

In the Timaeus, Plato presents time as a product of the Demiurge's craft. Contemplating the eternal Forms, the maker wishes the visible world to resemble them as far as a world in motion can. The Forms neither become nor pass away; the cosmos, by contrast, is generated and must move. Accordingly the Demiurge, when he sets the heaven in order, produces "a moving image of eternity," moving according to number. That image is what we call time.

On this account, time and the heavens come into being together. The sun, moon, and planets are instruments of time: their circular motions mark days, months, and years, so that mortals may number succession. Before the ordered motions of the heaven, there is, properly speaking, no before and after. Plato thus treats time not as a container that might exist empty of bodies, but as a numbered order inseparable from the celestial revolutions that measure it. The same passage links the question of time to those of Change and of Eternity: the truly real is unchanging being; temporal succession is the nearest the sensible order can come to that permanence.

Time therefore has a secondary, derivative status. It belongs to the realm of becoming rather than to the realm of Forms, and it is intelligible only by reference to the eternity it imitates. Plato also cautions against applying tensed language to what is eternal, as if the Forms themselves had a past or a future. Whether time could have a beginning, and whether anything can be said to "precede" the ordered cosmos, become permanent questions for the tradition that follows him.

Aristotle will press the account by asking what, if anything, precedes the Demiurge's ordering of the heaven, and by offering a definition of time as the number of motion with respect to before and after. Plotinus and Augustine will retain Plato's opposition of time and eternity while relocating time, in different ways, within the life of the soul. The debate over whether time began with the world, which Augustine and Aquinas treat in theological terms and Newton in physical ones, finds one of its earliest formulations here.

Aristotle's analysis of time in Physics IV begins from the difficulties that any account must face. The past is no longer, the future is not yet; the present seems indivisible, yet time is a continuous quantity divisible into parts. Time is not itself motion, for motions vary while time is uniform; yet time does not exist without change. From these observations he draws the definition that governs much of later discussion: time is the number of motion with respect to before and after.

Where there is change, we distinguish earlier and later moments; by counting these we have time. Time therefore requires both motion and a soul capable of numbering. Aristotle asks whether time would exist if there were no numbering mind, and leaves the question partly open: there would still be motion, and the before and after as attributes of motion, so that time might exist as these "qua numerable," even if nothing actually counted them. He also notes that time measures rest as well as motion, for what can move may be at rest, and rest, no less than motion, is in time.

The "now," for Aristotle, is both a division and a link. It is the end of past time and the beginning of future time, always the same in character yet always different in what it marks. Through the succession of nows, past and future form a continuous whole. On this view, time is continuous, without beginning or end in the natural order, and is measured by the regular motions of the heavens. The relation of time to motion, and the question whether either can have a first moment, connects his physics to the discussions of Change and of Infinity elsewhere in the tradition.

Aristotle's definition remains the standard philosophical analysis of time through antiquity and the Middle Ages. Aquinas will adopt it as the measure of changing creatures, while distinguishing eternity and aevum as further modes of duration. Augustine will take up the admission that numbering seems to require a soul, and will argue more fully that what we measure when we measure time is an impress in the mind. Newton's absolute time, flowing independently of any motion, will later stand as a deliberate alternative to the Aristotelian account.

Plotinus devotes the seventh tractate of the Third Ennead to eternity and time, and revises Plato's image while retaining its dual structure. Eternity, he maintains, is not endless duration but the whole life of Intellect possessed at once: complete, unbroken into period or part, without extension or interval. Time, by contrast, is the mode of life proper to Soul, which cannot possess itself all at once and must unfold its activity in succession.

When Soul turns from restful contemplation of Intellect and seeks to produce its own order, it generates time as the spreading-out of that activity. Time is therefore the life of the Soul in a movement of passage from one state to another: not primarily a number counted upon celestial motion, but the interior extension of a life that cannot remain gathered in the eternal now. The heavenly motions may still mark time for us, yet on this view they are secondary signs of a more fundamental temporal process in Soul itself.

The account thus shifts the locus of time from the outer cosmos toward the living principle that animates it. Eternity and time are related as Intellect at rest is related to Soul in motion; the contrast belongs as much to psychology and metaphysics as to physics. Plotinus thereby joins the discussion of time to those of Soul, Being, and Eternity, and prepares the way for a more thoroughly inward analysis of temporal experience.

Augustine will seize upon this interiorization, arguing that we measure times in the mind as memory, attention, and expectation. Later writers who distinguish lived duration from the mathematical measure of motion may be read as continuing, in different vocabularies, a line that Plotinus opens when he makes time the life of Soul rather than a mere attribute of the heavens.

Book XI of the Confessions is among the most sustained examinations of time in the tradition. Augustine begins from a familiar perplexity: if no one asks him what time is, he knows; if he wishes to explain it, he does not know. The past no longer is, the future is not yet, and the present has no extent of duration. Yet we speak of long and short times, and we measure time as it passes. How, then, can time be said to be, and what is it that we measure?

His answer turns inward. What we measure is not things themselves as they pass, but the impressions they leave in the mind. There are not properly three times, past, present, and future, but three presents: the present of things past, which is memory; the present of things present, which is attention; the present of things future, which is expectation. On this view, time is a distension of the mind, an extendedness of the soul rather than an independent feature of the outer cosmos. The discussion of Memory and Imagination is thus inseparable from the discussion of time itself.

Augustine also places temporal creatures beneath the eternity of God. God does not endure through successive moments; He holds all times in a single changeless present. Creation and time begin together: there is no time before the world, for time requires some creature whose motion can give birth to change. The puzzles of measurement, of the present's instantaneous character, and of God's priority to the world are treated together, so that the analysis of time opens upon theology as well as psychology.

Later writers inherit both Augustine's phenomenology of temporal experience and the tension he leaves between time as a measure in the mind and time as something the created world undergoes. Aquinas will try to restore a real measure of changeable things while preserving divine eternity. Newton will insist that absolute time flows whether or not any mind measures it. James, describing the specious present, will return in a psychological idiom to themes Augustine first set out.

Aquinas draws together Aristotelian physics and Augustinian theology by distinguishing three modes of duration. Time, following Aristotle, is the measure of motion and change, belonging to material things subject to succession. Eternity, following Boethius and Augustine, is the simultaneously whole and perfect possession of interminable life, belonging to God alone. Between them stands aevum, the duration proper to angels and separate souls, unchanging in substance yet capable of change in their acts.

This threefold scheme preserves the difference between God's eternity and any merely endless temporal series. Even if the world had always existed, Aquinas holds, it would not be eternal in the sense in which God is, for the divine being is all at once, without succession. As eternity measures permanent being, so time measures movement; the more a being recedes from permanence and is subject to change, the more it is subject to time. The intermediate mode of aevum accounts for creatures that are neither wholly temporal nor divine.

On the question whether the world and time had a beginning, Aquinas holds that reason alone cannot settle the matter. Arguments for an eternal world, including Aristotle's, he regards as dialectical rather than demonstrative; that the world began is known by faith. God's creative act is eternal, yet what is created may have a temporal beginning. Time is real as the numbered succession belonging to changeable creatures, and it presupposes the eternity from which creation proceeds, without being a container independent of the things it measures.

The synthesis shapes scholastic teaching on time, eternity, and the intermediate duration of spiritual creatures. When Newton treats absolute time as flowing without relation to any motion, and Kant treats the beginning of the world as an antinomy of pure reason, they re-open questions that Aquinas had assigned respectively to physics, metaphysics, and faith. The distinction between time and eternity continues to be treated more fully under the idea of Eternity.

In the Scholium to the Definitions of the Principia, Newton distinguishes absolute from relative time. Absolute, true, and mathematical time, of itself and from its own nature, flows equably without relation to anything external, and is also called duration. Relative, apparent, and common time is some sensible and external measure of duration by means of motion, such as an hour, a day, a month, or a year, and is commonly used in place of true time.

Newton's reason for the distinction is practical as well as philosophical. Men ordinarily conceive time only from its relation to sensible objects; astronomers must correct the inequality of natural days if they are to measure celestial motions by a more accurate time. Absolute time is the perfect measure of motion precisely because it does not depend on any particular motion. All motions may be accelerated or retarded, but the flowing of absolute time is not liable to any change. Relative time is measured by motion; absolute time measures motion without being itself a property of bodies.

This account departs from Aristotle, for whom time could not exist apart from motion, and from Augustine, for whom the measure of time is an impress in the mind. Newton's absolute time is an independent framework, infinite and uniform, in which events are ordered as to succession, just as bodies are ordered in absolute space as to situation. The parallel treatment of time and space, and the question whether empty time before or after the world is intelligible, belong as much to the idea of Space as to that of Time. Locke's duration, unbounded yet not extending beyond all being, and filled by God's everlasting existence, stands nearby in the same period.

Absolute time becomes the default framework of classical mechanics for two centuries. Leibniz will deny the need for such an independent entity; Kant will argue that if time is treated as a self-subsisting container, one is driven to admit two infinite nonentities existing only to contain what is real. Later physics will challenge the classical assumption of absolute simultaneity. Within the great books, Newton's Scholium remains the clearest statement of time as a mathematical magnitude independent of the motions it measures.

Kant rejects both the Newtonian view that time is an absolute reality and the view that it is merely a relation abstracted from experience. In the Transcendental Aesthetic of the Critique of Pure Reason, he argues that time is an a priori form of intuition: specifically, the form of inner sense, the condition under which we intuit our own states and, thereby, all appearances whatsoever.

All perceptions, outer as well as inner, are given in temporal succession. We cannot remove time from our representations as we can, in thought, remove particular objects; even when we empty intuition of all content, the form of time remains. Time is therefore transcendentally ideal, belonging to the subject's sensibility rather than to things as they are in themselves, yet empirically real, applying necessarily to every object of experience. About things in themselves we know nothing temporal; only appearances are in time.

This account is meant to explain how arithmetic and the necessity of temporal sequence can be known a priori: they describe the structure of our sensibility, not an independent order of things. Space, as the pure form of outer intuition, is limited to external phenomena; time, as the form of inner sense, is the formal condition of all phenomena. In the Transcendental Dialectic, Kant further sets the question whether the world has a beginning in time among the cosmological antinomies, where opposed arguments appear equally cogent and neither conclusion is demonstrated. The beginning of the world, which Aquinas had referred to faith, becomes for Kant a limit of theoretical reason.

Hegel will rework Kantian time by treating it as internal to the logic of nature and of Spirit rather than as a mere form of subjective intuition. James will describe the specious present without relying on transcendental deduction, yet will share the insistence that temporal experience must be analyzed from within. The older debate whether time is a container, a number of motion, or a measure in the mind is, on Kant's terms, redirected: time is neither substance nor relation of things in themselves, but the form under which anything can appear to us at all.

Hegel accepts that time is bound up with sensibility and with successive negation, but he refuses to leave it as a merely subjective form of intuition. In the Philosophy of Nature, time is the pure form in which natural being negates itself: each moment passes into what it is not, so that nature is driven beyond any fixed state. Time is thus the abstract negativity of the sensible, the element in which finite natural things show their instability.

In the Phenomenology of Spirit, time becomes the medium in which Spirit works out its self-knowledge. "Time is the concept itself that is there": Spirit appears in time so long as it has not grasped its pure concept, and history is the process by which that grasping is achieved. Temporal succession is not an external stage on which Spirit merely happens to act; it is the way substance becomes subject, the form in which rationality develops. When Spirit comprehends itself as absolute, time is, in principle, known and no longer merely suffered.

Hegel therefore binds the analysis of time to the philosophy of history. The division of world-history into epochs is not, for him, a mere convention of calendars, but follows from the dialectical triad that is the form of historical development. Temporal order, succession, and the contrast of ancient and modern, which other writers treat as conventional or astronomical, acquire for Hegel a logical and spiritual significance. The idea of Time here meets the idea of History, and the older question of time's reality is answered by making time internal to the process of reality itself.

Later historicist and dialectical philosophies take from Hegel the view that time is the element of development rather than a neutral container or a fixed form of the mind. Whether that development can be completed, and what becomes of temporal experience once Spirit is said to have comprehended itself, remain open questions for those who follow him.

William James treats the problem of time as a problem of experience. The time we actually live is not the mathematical instant of physics, a knife-edge without duration, but what he calls the specious present: a felt stretch of a few seconds, with a nucleus of immediate presence and vaguely vanishing fringes toward past and future. Past and future can exist for us only in some present; if the present had no breadth, extended parts of time could not be given in experience at all.

The unit of our perception of time is therefore a duration, not a point. We sit, as James puts it, on a saddle-back of certain breadth, looking in two directions into time. Change, motion, and melody are perceived as wholes already extended; we do not first have bare nows and then synthesize succession from them. Awareness of change is the condition of perceiving time's flow, and that awareness itself occurs within the specious present, whose content is felt as having one part earlier and another later. On the basis of experimental estimates, James takes this present to vary from a few seconds to not much more than a minute, with a nucleus of a dozen seconds or less.

He insists, against a purely subjectivist reading, that time relations are also impressed from without. Things sequent in time stamp their sequence on memory; the time and space in which objects exist are as independent of the mind as the objects themselves. The analysis is empirical and phenomenological rather than transcendental. James is skeptical of Kantian a priori deductions, yet he shares the inward turn: lived time must be described from within the stream of consciousness. The themes of memory, attention, and expectation recall Augustine, while the claim that duration is primary and the instant an abstraction recalls the broader opposition between experienced time and mathematical time.

James supplies the modern psychological description of the present as thick duration. Later phenomenology of time-consciousness develops related insights with different methods. Within the great books, his chapter remains the principal attempt to solve, in terms of experience, the old puzzle of how past and future can be present to a mind that never escapes the now.