Time is everywhere, but impossible to grasp: we talk constantly about it since our language is temporalized according to the past, the present and the future, we live it and experience it in the form of regret, promise, project, memory, surprise or expectation, we observe it in the stars, our bodies, the seasons. But we don’t know it. This ambiguous status of time has given rise to a philosophical questioning constantly taken up from the pre-Socratics to the present day. Every great philosophy deals with it. Several themes appear as so many open questions.

First, what is the reality of time? We can distinguish two main philosophical lines of thought that emerged from Antiquity. For the first, time is reality at once astronomical, physical and vital, which supports our temporal experience and consciousness. Thus, Plato considers that there are several real times: eternal for gods, cyclical for stars, linear for men and beasts who are transformed through metempsychoses. Subsequently, Descartes thinks of time as a continuous creation constantly replayed by God; Hegel sees in time the way in which reason is concretely realized: first through the nature time, then that of history and human consciousness. Bergson distinguishes between abstract, measuring time and duration, the only real that essentially characterizes the vital impetus unfolding in the universe and concentrating in consciousness which in turn can expand it to extract itself from the pure present and recapture the past, imagine the future or dream. Conversely, for Aristotle, time does not exist but only defines the measure of change: in reality, only individual substances exist. Some change more or less quickly according to becoming, generation and death, growth, movement; others, like the stars and the gods, always remain unchanged. Subsequently, Leibniz also considers that time is only the measure of the substances becoming: it only expresses order and succession without corresponding to any reality. Kant considers that it is only an a priori form of the subject’s sensibility: time then designates the simple framework in which we arrange a series of singular experiences according to a certain order. In turn, Husserl characterizes time as an essential dimension of human consciousness that thematizes objects in space and time without our being able to perceive either as such. However, phenomenological time is not a simple fixed frame as in Kant, but expresses a consciousness dynamic. Currently, the reflection avenues on the time metaphysics seek to understand the plurality of times of which the sciences speak: thermodynamics, quantum mechanics, general relativity, population genetics, embryonic development, neurosciences, computer science do not deal with the same temporalities. Rather than trying to unify them by reducing them to each other, a fruitful avenue consists in assuming that there are several times that are intertwined.

A second order of questions deals with time’s moral and political dimension. Every human being is part of a heritage that induces obligations or debts towards the past, in a present that binds him with his contemporaries through duties and opens up an uncertain future. Aristotle inscribes ethics in a becoming: everyone must practice becoming a virtuous man, as the zither player trains to play well. In particular, we must learn to decide in uncertain situations and according to a contingent future; how do I choose when I don’t know the future consequences of my actions? The virtue’s ethics consists in assuming this uncertainty, sometimes this worry, by accepting ignorance but by demanding to practice prudence as best as possible, i.e., forecasting art which takes into account the lessons of past and discerns certain demands in the hubbub of urgency. In a very different way, Kant considers that morality resides in duty’s respect, always and everywhere the same that can be formulated in an imperative absolute’s form: Act in such a way that your action’s maxim is universalizable. Whatever the circumstances, whatever the consequences, duty remains identical to itself, the eternal morality’s law. It is thus also a present’s morality, but it does not imply a becoming, rather an sempiternal duty recurrence, and not a becoming. Hannah Arendt rather develops the two other dimensions of the binding heritage and the uncertain future through a reflection on two human commitments: forgiveness consists in untying the other from the obligation he has created himself with regard to me. By inflicting a wound or an offense upon me, the other owes a debt toward me; I can free him from it if I agree to forgive him, to open up a present that no longer depends on the past. Conversely, the promise consists in tracing a safe path in the uncertain future: even if I do not know what tomorrow will bring, I can decide to commit myself and keep my promise whatever happens by agreeing to bind myself today towards others according to a determined period. Hans Jonas opened up new perspectives in introducing a duty towards future generations: we do not know who the men, women and children of tomorrow or of the fourth millennium will be, but we have a duty towards them to leave them a compatible world with the fulfillment of a truly human existence. I become aware of the time of the planet, of the living and of the ties that bind me to future humanity. As for politics and society, they structure the collective time organization: establishing timescales, regulating common time are among the sovereign functions. Formerly devolved to monasteries, then to towns and merchants, the time determination is now of the State responsibility, which determines the working time, the festivals and the memory they convey, the education age measurement, minority and majority, or retirement. But this sovereignty constantly encounters disputes, for example social, or resistance, for example economic.

A third-dimension deals more specifically with the consciousness phenomena: whatever the time’s objective reality, and even if we could never ultimately know what it is, we cannot deny existential or phenomenological temporality. We remember, we hope or fear the future, we exist here and now. Saint Augustine showed the essential link between this conscious experience and language, which remains our only time telling instrument. Often even this phenomenal reality of time determines our lives much more than ontological questions about temporal objectivity. Especially since this conscientious phenomenon of time is not reduced to the individual personal experience, but encompasses a collective experience: urgency and acceleration undoubtedly characterize our time trademark. While our technologies constantly assure us of saving time, we always lack it and live with the permanent feeling of scarcity. How can we slow down our rhythms of life today and regain slowness? Is acceleration a new form of alienation?

These surveys could be multiplied. Let us name a few other tracks: history determines our relationship to time. The way we write our past history offers a prism for understanding our present. We become aware of the structures that deeply determine us. Aesthetics offers particular experiences of time: listening to music, taking a photograph, representing an imaginary scene, reading a novel allow us to experience and explore different temporalities. Anthropology teaches us that other cultures live in very different temporalities from our linear progress and acceleration representation: they can be cyclical, presentist, decadent, slow, etc. Religion opens up yet another temporal dimension: as the etymology reminds us (temnô = to cut), the temple cuts out a particular space-time in society and existence. Through Shabbat, Ramadan or Sunday, rites redraw a common time for some who nourish a belief in eternity as the horizon of time.