The philosophy of space and time is a branch of philosophy that deals with problems related to the epistemological and ontological characters of space and time.
Fulfilling all the demands of nascent rationality, Greek philosophy is by nature allergic to time. In fact, in search of identities and permanence capable of providing thought with the fixed and stable benchmarks it needs, it is betting on Being against becoming. This is the very early position affirmed by Parmenides of Elea: “Being is, non-Being is not. The Being is uncreated, imperishable, still and eternal. We cannot say that it has been or will be, since it is both entirely in the present moment, one, continuous.” (The Way of Truth, § 8).
Heraclitus of Ephesus is the first philosopher to deal explicitly with time and to recognize its irreducible reality; but this is to deplore its flight, inconstancy and unintelligibility: “We bathe and we do not bathe in the same river” (fragment 12). “The cold becomes hot, the hot cold, the wet dry and the dry wet” (fragment 126). Time in turn brings opposites into conflict and harmonizes opposites and, as such, it clearly appears as the universal motor of nature. But it is just as much nonsense, because it violates the logical principles of identity.
This is why Plato, following Parmenides and the observation of Heraclitus, will introduce diversity and otherness into Being with his theory of Ideas. He speaks of time as “the moving image of the still Eternity.” That is to say, the imitation, in the order of material productions, of the instantaneous perfection of the intelligible model; the resumption of this in minor mode, through the endless deployment of circular and regular movement (“progressing according to the law of numbers” (Timaeus, 37 d).
Aristotle rejects this conception of a transcendent world of intelligible and eternal Ideas to be interested only in the way in which matter takes shape in our immanent world of things. Because, in this world in the making or in this moving nature, everything is in the power of something else until it finds and realizes its own form. This is to say that, for the physicist Aristotle, time is the motor of things or the force of life which circulates in the great body of nature. He defines it as “the number of movement according to before and after” (Physique, IV, 219 b), that is to say as what is measurable and measured in the movements (or changes) between two instants (one anterior; the other posterior) taken as reference points. As we can in fact only enumerate things of the same nature and yet distinct, time has this double property because, in it, all the moments are alike in their function of separating the before from the after and, however, in their indefinite succession, they remain quite distinct; the one before is never confused with the one after. For Aristotle again, if time is used to enumerate all kinds of movements, the reference time, universal time, is that of the uniform circular movement attached to the sphere of fixed stars. For him, therefore, there is no doubt: time is a property of nature. Nevertheless he recognizes that, time being number, it can only exist in the soul and by the soul because the numbers have only intelligible or mental reality. “What is problematic is to know whether, yes or no, in the absence of the soul, time could be … If nature only grants the soul the faculty of numbering, and more precisely in this part of the soul which is the intellect, it is impossible for time to be without the soul, except as regards its substratum, in the sense that it is said that movement can be without the soul.” (Physics, IV, 223 a). A man alone, therefore, as he is endowed with a soul, can think and imagine time. But that does not prevent time from being an objective reality.
It remains that Aristotle suggests a new problematic, psychological and no longer physical. Time of the soul differing from the time of nature; human time and world time. We find these two times, physical time and lived time, closely linked in Stoicism. For the Stoics, in fact, time is (like void and place) an “incorporeal”, that is, something which has a virtual existence more than a real one (which is reserved for bodies). More exactly, it is the interval in which a body will deploy its action or its process (just as the “void” is the interval in which a body will take place and delimit a “place”, by incorporating itself into it and giving it body somewhat at the same time). There are therefore also two times: the pure indefinite interval, virtually ready to welcome the manifestation of a body (in ancient Greek: αἰών); the interval effectively delimited by the process that takes place there. That is to say that, determined by the presence in it of a body, time is essentially present, the past and the future extending indefinitely to the margins of it. Thus in physics, cosmic time is that of the All of the Universe which, caught in the cycle of “eternal return”, is destroyed and regenerated periodically. It derives its reality from the vital breath which animates the whole of nature and from the periodic return (the “Great Year”) which gives it relative stability. But as the All is only the expression of the Logos or of the God who ensures the coherence and the harmony of all its elements, we can say that cosmic time is the tension of the Soul of the World; that, for the latter, it is entirely present; and that it appears successive, disappearing at its two ends in the mists of the past and the future, only at the fragmentary view of human individuals … But isn’t the vocation of the sage to rise up to the contemplation of the All and to reproduce its harmony in one’s own life (“to live in accordance with nature”)? Physics therefore leads to ethics: we must understand and want the order and necessity of the world; you have to want things to happen as they are; one must, with all the strength of one’s soul, adhere to what is and make virtue and freedom of necessity. By his effort to respond “present” to everything that happens and to adhere to events, the sage participates in some way (hic et nunc, here and now) in the cosmic present and in divine beatitude. By the tension of his soul, he infinitely expands the ephemeral instant, he holds together all that composes it and he can thus stop the hemorrhage of becoming in order to enjoy in time a true fullness of being. From a given and a natural fatality, it was the subject of a psychic and moral recovery and thus converted a time marked by flight and non-being into a block of affirmation that has the brilliance of eternity.
For Plotinus, too, the nature and origin of time has more to do with the Soul than with material things. Not only does Plotinus refute the Aristotelian theory of time as a number or measure, but he considers it a mistake to seek time exclusively in motion, for the latter is only one aspect of it, and not the most important. He prefers to return to the Platonic definition of time as a “moving image of immobile eternity” … reinterpreted in a very personal way. Indeed, in the “procession” of the “hypostases”, time appears with the Soul (third hypostasis), when the latter turns away from the One and the Eternal Ideas to generate the sensible world in Matter. Time is therefore first of all a degradation of eternity. Between the positive immobility of perfect beings (who, being everything, lack nothing and want nothing) and the negative immobility of beings deprived of everything (who, being nothing, also lack nothing and want nothing neither), the incessant mobility of time corresponds to beings who, not being perfect, nevertheless admire perfection and seek to achieve it in their own way: namely step by step, part by part, patiently, continuously, indefinitely. “This is why time comes into the world at the level of the Soul, which by contemplating the motionless beauties of the intelligible sphere awakens, desires, stirs, like the chrysalis which gradually fills with life while deploying organs and sensitive incarnations. ”
So if the Soul of the World breathes both time and life into everything it animates, it does so, among other things, in the movement of the sky and the rotation of the stars, where time is particularly evident. And that is why the revolution of the sun is used to measure it, and the alternation of day and night to delimit its interval. But we should not believe that it is these movements which generate time; no, it is the Soul of the world … and also all other souls, especially the individual souls of men, who are one with it. Vital dynamism, time is of a mental or spiritual nature more than physical or material. And while it’s just a pale imitation of eternity, so it has its positivity too. But above all, if time does take us away from the One and from eternity, it is also there to lead us back there; the path is the same, which tumbles down and goes up. Helpful as well as fatal. The soul, in fact, by reflection, concentration, contemplation, can convert the movement of procession and dispersion and, gathering its forces, undertake the ascent towards the Principle of all things … until exceptionally merging with it in mystical ecstasies.
But it is above all another heir of Plato, the Christian philosopher Saint Augustine, who will complete a psychological analysis and definition of time. With the advent of Christianity, a radical paradigm shift has already taken place: in circular time, which took its references in the cycles of nature, a linear time has been replaced, adapted to the historical narrative and to the messianic expectation. . The time of men has made its entry on the scene of the world … entry sufficiently shattering to scandalize a Greek head like that of Plotinus, who cannot admit that time has a beginning and an end and, between the two, an incredible story made faults, punishments, alliances, incarnation, redemption, resurrection and other similar events (Against the Gnostics). But it is in an even more radical way that Saint Augustine reduces time to the dimensions of man. Starting from the ordinary division of the past, the present and the future, he shows that in itself time does not have to be: the past because it is no longer, the future because it does not exist, he is not yet and the present because, like a stillborn child, it only comes into being by ceasing to be ipso facto. Then, analyzing the banal experience of measuring a duration, he points out that what is thus measured is the persistence of a memory. For the past objectively disappeared always exists in memory, just as the future already exists in our expectation and as the present itself, so volatile, acquires some depth in our effort of attention. So what we are measuring is not a movement, as Aristotle believed, but a mental impression. If therefore time is indeed a kind of interval, it is not in an objective sense external to us, but in the sense of a “stretching” or “distension of the soul”. The human soul, in fact, is not content with passively adhering to the real as it is given to it in the instant; he is active. He anticipates and waits; he preserves and remembers; he makes himself available and attentive. And it is through these three activities that it generates the future, the past and the present respectively. “From which it follows for me that time is nothing more than a stretching. But a distension of what, I don’t know exactly, probably of the soul itself. ” (Confessions, book eleventh, chap. XXVI). However, from God’s point of view, what stretches thus for us in time is grasped instantly, in the oneness and stillness of eternity.
In modern times, the philosophy of time will oscillate between the two poles of realism and idealism. Realists give time (as well as space) an existence of its own, independent of the human mind; idealists challenge or question this independent existence.