On Time

Students must not die before their teachers. Krzysztof Michalski was my student at Warsaw University for two years, between 1966 and 1968, and he wanted me to supervise his master’s thesis. It turned out to be impossible because in 1968 I was expelled from the university. But we kept in touch. I remember animated discussions among a small group which met at Krzysztof’s initiative in the early 1970s in Warsaw, in a flat of one of his friends, in order to stabilize the Polish translation of Heidegger’s terminology. One of the participants was father Józef Tischner, whom I met then for the first time. In 1971 Jan Patočka came to Warsaw to give a lecture on Husserl at the Polish Philosophical Society. After the lecture, a select group of listeners had dinner with him. I was always convinced that Krzysztof was there, among us, and that it was the beginning of his admiration for Patočka. But two years ago he wrote to me saying that he did not remember the event, so now I’m less sure.

My departure from Poland did not interrupt our exchanges. In 1975 he organized a debate on Heidegger in Znak, a Catholic monthly published in Krakow. I contributed with a paper sent from France. Two or three years later, we spend a couple of days together in Dubrovnik, where he ran an international seminar with, among others, Hans Georg Gadamer. In the 1980s, we met in Castel Gandolfo, where he organized symposia with the Pope, and in Paris, as well as here in Vienna, during my trimester at the IWM. After 1989, we met several times in Warsaw. In 2007, we were both in Oxford for the eightieth birthday of Leszek Kolakowski, and had the opportunity to meet a year later here, and then in 2009 or 2010 in Warsaw. It appears from our exchange of mails that we tried to meet in Warsaw again a year later. To no avail. Therefore I was looking forward to meeting Krzysztof here today. Since I was unaware of his illness, the unbelievable news of his death came as a shock.

This is to say that Krzysztof was a part of my life. This is also to recall Krzysztof’s activities, albeit only the small part I was involved in, and the names of some of the people who were important to him. They were not that numerous. Krzysztof set very high standards in philosophy and in intellectual and spiritual life more generally. Intellectual and spiritual because these two dimensions were for him inseparable. His confrontations with philosophers of the past were always analyses of their ideas and personal meditations.

For a collection of essays by Heidegger that Krzysztof published in 1977 he borrowed the title Budować, mieszkać, myśleć (“To build, to inhabit, to think”). These three verbs could have been chosen as the motto of his life. He was a builder, as the IWM demonstrates. He was a thinker, as his books and papers demonstrate. And he was an inhabitant – of rather, a citizen – of the world, who felt responsible for it and tried to improve it in his area of competence to the best of his abilities.

Students must not die before their teachers. When they do, it’s scandalous in the proper sense of the word. It’s something one cannot reconcile oneself to. And which leaves survivors, for the rest of their days, with this appalling and implacable fact.

I dedicate this lecture to Krzysztof’s memory.

*

Before asking “What is time?”, let us start with a description of how we deal with what we are used to calling “time”, without any advance assumption about it. We know four ways of dealing with “time”. I’ll call them families of temporal practices: chronometry, chronology, chronography, and chronosophy. Please keep in mind that, in what follows, the word “time” will be used in inverted commas to avoid the repetition of the formula “that which we call time”. When we are entitled to speak about time without inverted commas, it will be clearly stated and justified.

“Time”, then, is something we measure. We do it constantly, without thinking about it. For this purpose we use clocks, which have an extraordinary variety in their external appearance, their display, their medium (digital or analogue), their level of precision, their inner architecture (mechanical, electronic, “atomic”), their positioning (fixed on walls, on the wrist, in fobs, in mobile phones, in cameras, in computers, etc.). We transport these clocks with us on the Earth’s surface, we send them into space and drop them into the ocean’s depths. We usually keep them for long periods: there are some clocks, actually quite numerous, that are used by successive generations. All this presupposes that “time” has the following features: it’s the same everywhere; it does not change; it’s uniform; it’s quantitative, which means that it may be divided in stable units of definite length, which may be in their turn divided in still smaller units (there is probably a limit to this but it’s unimportant for everyday life); it has a circular structure (from 0h0’0’’ to 0h0’0’’) and hence it’s not linear and has no direction.

But we not only measure “time”. We also determine our position in it. For that purpose we use calendars. When I say that today is April 18, 2013, I determine my position with respect to three reference points: the initial event from which 2013 years have passed, the beginning of the present year, of which it is the fourth month, and the beginning of the present month, of which it is the eighteenth day. This obviously resorts to units of measurement of time: years, months, days. But I do not use them in this capacity: I take them as granted to say where I am. The same occurs when I look at my clock to find out the hour of day. I don’t measure anything, I just determine my position with respect to a reference point. The chronological systems in use throughout the world are very varied and in general are connected to religions. Our year 2013 roughly corresponds to the Muslim year 1434/1435 and to the Jewish year 5773/5774. Roughly, because these years begin at different dates and have different lengths; the same holds for the division in months and the definition of the day. In contradistinction to chronometry, chronology does not assume that “time” is the same everywhere – it is different according to chronological systems – or that it is uniform: in each system it has a singularity, an initial event against which years are counted.

There are other singularities: the beginnings of each year restart the count of months, and feasts that return each year but not necessarily on the same date. Moreover, units in which this “time” is divided are not identical; even our years do not have not exactly the same length– leap years have one day more than other – and the same applies to our months. Strictly speaking, therefore, the “time” of chronology is not quantitative; it is quantitative only approximately. It’s also a linear “time” described by a series of numbers going from 0 to N. And it’s irreversible: once passed, April 18, 2013 will never return. In this frame, therefore, it is possible to distinguish today from yesterday and tomorrow, the present from the past and the future. Last but not least, the “time” of chronology seems to have a direction defined by the increasing distance from the initial date. It follows that the “time” of chronology is different from that of chronometry, despite all efforts to harmonize them.

In the background of the “time” measured by clocks and of that with which we determine our position using calendars, there is the lived “time” filled by the succession of events, of changes in the state of our own body or of our environment, perceived through internal or external senses. This “time” seems to us in some circumstances very intense, hectic, when events jostle with each other; in other circumstances, it seems very slow, monotonous, when nothing or almost nothing happens. These events affect us to a very variable extent and they have different durations. Some are related to events that occurred earlier; others seem to herald those which will arrive later. We therefore distinguish in lived “time” between a present moment corresponding to events we are actually perceiving, a past composed of events preserved in memory, and a future containing events which await us. And we register events that we wish to preserve in memory in our calendars or private diaries; this is the lowest level of chronography. As a description of events, be they those of an individual’s life or the life of a collectivity, chronography may do without the “time” of clocks and calendars, even if nowadays we are inclined to note the day and in some cases the hour and even the minute each event occurs.

As determined by a succession of events, the “time” of chronography is neither the same everywhere nor uniform. It varies according to individuals and collectivities. It varies, moreover, according to the density or rarity of events. As far as an individual is concerned, this “time” is lived as linear and oriented in a definite direction, because it is inseparable from coming of age and from growing old. But even in the case of an individual, it is not completely irreversible; some events may repeat themselves, if not exactly as they were then at least in a very similar form. As far as a collectivity is concerned, this “time” may be treated as linear or cyclical or oscillatory; in the first case, one may ascribe to it a direction. It depends, at least partly, on collective beliefs: myths, religions, ideologies. All of them have an idea of “time”.

This leads us to the last family of temporal practices: to chronosophy. This term denotes attempts to think “time”: to assert its reality or, on the contrary, to claim that it is only an illusion; to oppose it to timelessness or to eternity or, conversely, to state that these categories are meaningless; to grasp “time” in its integrality, to try to provide a definition of it or to conceive the past, the present, and the future together. Such attempts to treat “time” as a whole characterize chronosophies inherent in monotheistic religions, according to which God, placed outside “time”, in eternity, knows “time” from its beginning to its end in the minutest detail; it is He who reveals the future to prophets and enables them to disclose it to their peoples. Taken as a whole, this “time” is endowed with a direction and sometimes with a limit; it is presumed to begin and end with the world. If religions assign a future which allegedly already exists to the gaze of God alone, then attempts to know what future we are actually preparing for our descendants – and what future we ought to be preparing for them –seek their legitimacy not in religion but in science. So it is with different demographic and economic forecasts for the next tens of years. So it is with the attempts of astrophysicists and cosmologists to determine the future trajectory of the universe. So it is with ideology of ecologists, according to which a major catastrophe is due quite soon: the Himalayan glaciers risk melting by 2070. And there are still many people who remember the “scientific” demonstrations of communism’s future victory over the world. “Times” of religions and “times” of ideologies differ greatly, but both differ even more from those “times” we have discussed so far, since they are principally characterized by their directions: up or going down, progressive or regressive, heralding an Edenic future of forewarning an Apocalypse. The “time” of religions is purely qualitative. Ideologies, when they pretend to scientificity, try to quantify the “time” they are speaking about. Here and there, “time” is not uniform and it is punctuated with events, some of which are more important than the other, enabling “time” to be divided into periods which are qualitatively different and of varying length.

Each one of the four families of temporal practices we have discussed ascribes different characters to what it calls “time”. Hence some questions. Do these four families deal with the same object or with four different ones? If they are dealing with the same object, why are there four different approaches? And if they are dealing with four different objects, why do we give these objects the same name? Moreover, what is this object? Is it only an intentional object, an object of thought, or does it have a reality and, if so, what kind?

To begin with, let’s look more closely at what we are doing when we measure “time”, when we determine our position in “time”, when we describe the succession of events which fill “time”, and when we ascribe to “time” qualities, directions or divisions. This “we” refers to all of us, since we all practice chronometry, chronology, chronography, and chronosophy in so far as we use watches and agendas and try to plan our families’ futures. It is true that we do it in different ways and that one can divide all societies into categories according to ways of managing “time” and to individuals’ capacity to master their “time”. It is also true that in our society there are individuals who live, as one use to say, “outside time”: without watches, without diaries, without projects. And it is true that a considerable part of the world population is living in such a state, even if one must qualify this statement because of the massive use of transistor radios and of mobile phones which serve as clocks. Be that as it may. In developed, post-industrial societies, the “we” that is used here applies to the immense majority of the population. But it applies also to these societies taken collectively, for they have created institutions in charge of the definition of the second and the indication of the hour, institutions which impose one or another chronology, divide the year into weeks and months, distinguish holidays from working days, determine the part of the day devoted to work and the length of vacations, and so on.

So, what are we doing when we measure “time”? We look at our watch and to ensure that it works correctly, we listen to the radio; if necessary, we put it right according to indications of the latter concerning hours, minutes and seconds. Radio in its turn is connected to a reference clock located in a physical lab, because the second – the basic unit of “time” –has been defined since 1967 as a “duration of 9,192, 631, 770 periods of radiation corresponding to the transition between hyperfine levels F=3 and F=4 of the fundamental state ⁶S_1/2of the atom of cesium 133”. I wonder whether my translation of this definition from French into English is correct and, moreover, I do not know what “hyperfine levels” are, or how to distinguish a “fundamental state” of an atom from a non-fundamental one. I presume the same is true of you, my dear audience. But what is important here is one and only one point: that the speed of the movement of the hand of my watch is connected, through the agency of the radio, to the speed of the reference clock. This means that the interval between two movements of the hand of my watch or between two successive digits coincides with the multiple of the period of radiation of the atom of cesium 133 when one of its electrons jumps from one level of energy to another, this multiple being the standard of the measure of “time”.

Let us note in passing that this assumes that the duration of the period of radiation defined above does not change from one second to another–an assumption that leads to an interesting philosophical question asked by Henri Poincaré. Why do we have to accept such a hypothesis which we cannot ultimately verify? We can only compare reference clocks with one another, which is already progress with respect to the epoch when there was only one reference clock, the astronomical one. According to Poincaré, the stability of the second is accepted by convention, which hence lies at the very foundation of the measure of “time”. Now, whoever says “convention” admits that, at least in theory, one can replace it with another convention – but would any physics be conceivable if we assumed the instability of the second? Poincaré knew that one can try to justify the hypothesis of the stability of the second using the principle of sufficient reason: in absence of any observable factor that interferes with (in our case) the period of radiation defined above, there is no reason to assume that the next period will be different from the previous one. But he considered this argument too weak to be convincing. Nowadays, because of the importance in physics and in philosophy of the principles of symmetry and hence of the principle of sufficient reason, the latter seems to me to be a much better justification of the stability of the second than a conventionalist idea.

It was only a digression. Let us come back to our essential point: that to measure “time” is to establish such a relation between two movements, the movement of the hands of my watch and the movement of the reference clock that the speed of the former must be equal to the speed of the latter. In other words, to measure is to coordinate these two movements with respect to their speeds. And now, what am I doing when I am determining my position in “time”? To find out today’s date, I take the calendar or the agenda and I look for the appropriate page, turning over or tearing out previous pages. In order to obtain a correct result, the number of pages I turn over or tear out must correspond one-to-one to the number of days, that’s to say of sunrises and sunsets, since the beginning of the year. In other words, the movement of turning over or tearing down must be coordinated with the apparent movement of the sun. But now this coordination is not with respect to the speed. It consists in making coincide one-to-one the beginnings and the ends of two intervals. I do exactly the same thing when I determine my position in the series of years, with the difference that, on the one hand, I now no longer turn over or tear off the pages of a calendar but replace one calendar with another and therefore continue a process which started well before my birth; and, on the other hand, I make the number of these calendars correspond not to the apparent movement of the Sun but to the number of complete revolutions of the Earth around the Sun.

Now, what about the recording of events as they come? In itself, this has nothing to do with “time”. What happens, however, when these events are related to one another through indications such as: “this one is earlier than the other”; “this one has some feature more intense than the previous one and less intense than the next”; “between this one and the following, several days (or years) have passed”? Or, what happens when a series of events is related to another series of events by a statement that one is denser or more rarefied than the other, which means that in the same interval (which one must first fix the length of) there are more events than in another of the same length, or that in one interval events follow one another side by side and in other interval of the same length they are separated by voids? Or when a series of events is related to another series of events by yet another statement: that in one interval later events have some feature that is more intense than in earlier ones, and in the other of the same length the reverse is true? What happens when a date is assigned to each event? If each event is perceived as a change, we are dealing in all these cases either with a coordination of changes which organizes events in a series, or with a coordination of two or more series of changes, or with the coordination of a series of changes with movements. This being so, we are in a situation similar to earlier ones with an importance difference: in this case, coordination has nothing to do with speeds or even with countable intervals (aside from the case of dating).Coordination concerns not movements but changes and it focuses on their qualitative features: density or rarity, continuity or breaking off, stronger or weaker intensity and hence, also, possible reversals of direction and presence of singular points where such reversals occur. We proceed also to such coordination inside one series with respect to qualitative features, when we state that the present is better (or worse) than the past, or that the future will be a repetition of the past, or that it will repeat it only to some extent.

Every one of us, without knowing it, coordinates movements or changes one with another. Every one of us, in doing so, plays the role of a coordinating agency. But human individuals are not the only known coordinating agencies. Moreover, as coordinating agencies, we individuals do not even depend on ourselves. We have already seen this when we spoke about temporal practices and the fact that we were obliged to refer to the hour given by the radio, to a chronological system received from ancestors, to events which occurred in our environment, and to collective beliefs: myths, religions, ideologies. This means that we are ourselves coordinated with ourselves and with other people by this superior coordinating agency, namely the society we are living in.

An entire system of institutions looks after different movements and changes, which together represent what we use to call “social life”, in order to prevent them diverging from another or that some of them enter in collision with others, which would be even worse. The calendar that imposes the same count of years upon all of us, that draws up the list of public feasts and distinguishes holidays from working days; the International Office of Weights and Measures, which preserves the standard of the second and therefore of the hour, to which all clocks in all countries are tuned; rules that define the length of the working day, the number of working days in any week and the length of periods of rest; public clocks; innumerable timetables; the opening of offices, of lessons at school and courses at university, the timetables of trains, buses, planes; our diaries, watches, TVs and radio sets, mobile phones, computers, and so on an so forth – it is thanks to all these institutions and devices, connected through the network of distribution of electricity, through radio waves, through cables and optic fibers that transmit signs, sounds and images, that social life unfolds almost smoothly.

But society is not a self-sufficient coordinating agency either, for it depends upon another agency: the Sun which imposes the alternation of days and nights, the rhythm of the seasons and the periodic, albeit irregular arrival of meteorological, biological and climatic phenomena. All this is known enough to free us from the duty of repeating it here. But it may be useful to recall that our organisms have internalized the apparent movement of the Sun in the guise of circadian rhythms, which express the coordination of the functioning of our organs by the suprachiasmatic nucleus of the hypothalamus, which receives signals sent by cells of the retina depending on ambient luminosity. The pineal gland transmits these signals to internal organs through the secretion of melatonin. It also may be useful to recall that it is the Sun which to a large degree regulates the rhythm of our societies, despite their emancipation from it to some extent. Artificial lighting permits the blurring of the boundary between day and night, while quick transportation and technologies of freezing permit smooth differences between geographical zones and between seasons. Despite all that, the alternation of day and night and the rhythm of seasons still determine the frames of social life.

We started with a description of what we do with that unknown entity we use to call “time”, without any advance assumption about what it may be. And we have arrived at the conclusion that all operations we have described may be subsumed under one heading. Each of them, indeed, is tantamount to coordinating two or more movements or changes. But they differ from one another because they coordinate different characters: in some cases there are speeds, in other cases there are qualitative properties such as continuity and discontinuity, uniformity or diversity, cycle or linearity, direction going up or down, and so on. And we have established that every human individual is a coordinating agency but not the unique one. Every individual is coordinated with other individuals by the society he or she is living in, which is therefore a superior coordinating agency; and every individual and every society is coordinated by the Sun.

Let us now remove the inverted commas from the word time. We can now state that what we are used to calling time is a coordination of several movements or changes by a coordinating agency. This justifies the use of this word because we know henceforth what we are speaking about. This makes possible an understanding of some of the difficulties one encounters when one deals with time. First of all, we can understand that in distinction to movements and changes, which are visible or observable, time as such is not and cannot be, for it is a placing into relation of these movements or changes – a placing into relation whose physical medium is all that we can observe. The Sun, for instance, coordinates living beings and human societies, among other things, through the agency of energy emitted in the form of light; we see the light but not the coordination itself, just as we see on the dial of the watch indications to which we adapt our behavior, without seeing the coordination established in that very moment.

This being said, let us stress that any coordination has a physical medium. Because of that, time belongs to physics. But it does not belong to it exclusively. There are also biological coordinating agencies, like the hypothalamus in mammals; time belongs to biology too. And because there are psychological and social coordinating agencies, it also belongs to psychology and sociology. To say that time belongs to physics, to biology, to psychology, means that one accepts all the consequences of that. And there are many. First, time is taken away from metaphysics, even if, as we shall see, ties between them are far from being cut entirely. Second, we are obliged to treat every coordination as an action governed by laws of physics, which means in particular that it cannot be instantaneous. Another difficulty we may consider as solved results from the different characteristics of time peculiar to chronometry, chronology, chronography, and chronosophy, and more generally from the plurality of ideas of time we are confronted with. Characteristics of time peculiar to different temporal practices are different because these practices coordinate changes or movements with respect to their different properties. And the plurality of ideas of time results simply from the plurality of coordinating agencies, which differ with respect to their nature and their functioning. We have already seen some examples of that.

The question may now be asked: why are we speaking about time when in fact we are dealing with the coordination of movements and/or of changes? First of all, because of the tradition to which we owe the questions we are trying to solve. But there is also a deeper reason, related to our own historical position. To conceive of time as coordination became possible only after the instauration of quantitative time and the disconnection of it from God, in order to treat it as a physical, biological, psychological, social, or cultural fact. All that happened only very recently; roughly speaking during the last three centuries. And then, there is also an inveterate tendency to conceive time as a flux, inbuilt in metaphors used in speech and writing, inbuilt also in our perception of ourselves as changing with the passage of years, and inbuilt moreover in a rich set of ideas of evolution and of history. Now, to say that the word “time” is the name of a coordination of movements and/or changes is tantamount to saying that it is not the name of a flux. Movements and changes have directions and these may be coordinated. In this view, time is a coordination of these directions and itself seems to have a direction. But that is not the case. The coordination remains invariable, in contradistinction to the agency that established it, which may change because, among other things, it is dependent upon superior coordinating agencies. Indeed, as we have already established, there is a hierarchy of coordinating agencies.

In this hierarchy, the Sun is obviously not the ultimate coordinating agency. It is just a star, a yellow dwarf whose changes conform to the stages of stellar evolution. Are these changes coordinated with the changes of other stars by an agency that acts at the level of galaxy or the universe? I am not competent to give an answer. It is clear, however, that the question of the ultimate coordinating agency, if we agree that it may be legitimately asked, leads us beyond physics toward theology. Such a coordinating agency is conceivable, indeed, only outside the physical universe, and hence outside all movement and all change. This also means: outside time. It is conceivable, in other words, only as the entity we call “God”, without really knowing what this entity is and to which we ascribe the unique privilege of being outside time, which we call eternity ,again without having a clear and positive idea of what that is. Asking this question means, let me repeat, positing an agency outside time, which nevertheless acts on time in so far as God is supposed to be the origin of all movement and all change. Time therefore acquires a double nature that is both indissolubly physical and metaphysical. As for me, I follow the illustrious example of Laplace, and do need not this hypothesis, despite mine not being satisfied by what I understand from my amateurish readings in matters of cosmology.

Let us now leave metaphysics and turn towards history. Indeed, as a psychical and social fact, time has a history. This history has already been summarized at the beginning of this talk, when I described four families of temporal practices. If we try to place these families in a common chronological framework and to ascribe to each the place which corresponds to its emergence, we see that chronometry was born recently, in the 14^th century, with the arrival of mechanical clocks. It arrived long after chronology, born with the sacred kingdoms of the ancient Near East and ancient China around the 3^rdmillennium BCE, probably along with writing and chronography. Chronosophy is even more archaic; its most ancient known examples are myths transmitted orally which tell the origins of the world and of humans, explain their present and announce their future. The four families of temporal practices may therefore be treated as four strata deposited in the course of history which provide us with access to the past, sometimes even a very distant one, through the remains it has left. The word stratum must be taken here in its literal meaning, not as a metaphor. It refers to strata which are quite real and which we can distinguish among objects, images and writings, some of them accumulated in situ, others in museums, collections, libraries, and archives, and others in the ideas, concepts, and mental habits of our minds.

A similarly stratified structure reveals itself when we look at each family of temporal practice in order to locate within a chronological framework the different practices that belong to it. To begin with chronometry: high precision time (to the fourteenth decimal place) arrives after a less precise time measured to about a second, which in turn arrives after a time measured in hours and minutes. The time of clocks arrives after solar time, which means that quantitative time arrives after qualitative time. Besides, the time of clocks has a history which is much more than that of an increasing precision. It is also a history of the disconnection of the time of clocks from the movement of the Sun and of its coordination with an atomic clock. This entails the reversal of relations between the hour and the second. The second is no longer a division of the hour but the basic unit of which the hour is a multiple.

The history of chronometric time is, moreover, the history of an object, the clock. Originally heavy and difficult to move, clocks were later made portable due to a series of technical inventions, but were still rare, costly and considered as a luxury. Finally, after another long series of technical inventions, clocks became everyday objects, at least as mass produced and hence inexpensive specimens, as opposed to those that attain stratospherically high prices. The history of chronometry is, in other words, a history of democratization of quantitative timetogether with its propagation in all fields of social life, in particular the workplace; ultimately even the work of the farmer became disconnected from solar time, which a century ago still regulated chronometric time in developed countries. And it finally, though I do not pretend to be exhaustive, it is a history of transition from the plurality of local times without any link between them to a unique global time divided into time zones – a history of the transition imposed first by railroads and later by the air traffic and made possible by the transatlantic telegraph and later the radio.

This does not mean that qualitative time has disappeared. It is always here and must be here because it is the time of life – the life of every organism and of every human being with its flux of emotions, perceptions, needs, desires, thoughts. Qualitative time is inherent to nature. Quantitative time is an invention of men, who have afterwards found in nature phenomena that act as clocks. Hence, the problem of the dominance of quantitative time over social life, result of the articulation of this time upon qualitative time. It is not an abstract problem. It must be solved everyday by all those who are obliged to adjust their biological rhythms to the time of clocks: cosmonauts, pilots on long flights, people working according to “three times eight” system, travelers who cross several time zones, in a word, by millions. Another peculiar case of this problem had to be solved when the decision was taken to quantify the solar year more exactly than previously in order to replace the old Julian calendar with the Gregorian one.

I cannot go into detail about the stratigraphy of chronology and chronography. Just few words to show that both changed. Christian chronology, which is still ours, had to be synchronized with other chronologies when Europeans discovered and started to study civilizations different from theirs. And it became a global chronology to the extent that it was accepted on other continents following the European expansion. Only a few countries today do not refer to it. But during this process, this chronology lost its Christian character to become a common era. It was extended to periods before the invention of writing, thanks to advances of dating using various scientific techniques, above all atomic physics. Chronology is no longer limited to human history; geologists and paleontologists applied it to the history of Earth and of life. Later strata brought in travel, colonization, archaeology and other sciences were therefore superimposed onto the ancient stratum of Christian chronology, which itself changed significantly during the millennial history of Christianity.

Chronography changed even more. A chronicle such as one wrote in the 15^th or 16^th centuries had very little in common with today’s monograph of economic of demographic history, with its battery of maps, graphics, and tables of numbers, if not equations. In between there came the antiquaries and scholars of the 16^th to the 18^th centuries: the Bollandists and the Maurists, Du Cange, Bayle, Leibniz, Leclerc, and Muratori; the historians of the Enlightenment: Voltaire, Gibbon, Robertson, Schlözer, Heeren; the historicism of Ranke and his German and Italian followers; the history of civilizations, with Guizot, Buckle, and Lamprecht; the political history of Tocqueville, the social and economic history since Marx through Pirenne, Rostovtzeff, the Annales school and Kula up until contemporary economic history and the new political and cultural history of recent years. The history of history since the 15^th century may be summarized still otherwise. In the 16^th and 17^th centuries, it was the propagation of the study of the past through sources, principally written ones, but as so far as antiquity was concerned also objects. In the 18^th century, it was the clarifying and application of principles of historical synthesis in the guise of the “philosophy of history”. Romantics later nationalized history and presented series of facts in the form of narratives organized around the conflict of classes or of states. In the second half of the 19^th century, positivist history required the strict application of the principle that the past be studied exclusively through written sources, and that all other forms of research on it be left to archaeology and anthropology. This principle was contested by the 1920s and in the course of the 20^th century there was an enormous enlargement of the repertory of historical sources, with the entrance of natural facts, of material discovered during diggings, of images, of visual and sound recordings, and so on.

And so finally we arrive at chronosophy, to discourses on time. One usually starts here, but I shall end with it, my purpose being to speak about time and not about opinions professed about it. These opinions are, however, too important to be passed over in silence and too complex to be presented chronologically in all their niceties. I shall therefore divide their long history in three epochs: that of qualitative time, when the measure of time occupied only a marginal place; that of quantitative time, following the invention and the propagation of mechanical clocks, when some thinkers tried to treat qualitative time as insignificant; and the epoch during which the problem of the relation between qualitative and quantitative time emerged center stage. The first lasted from Antiquity to the 17^th century; the second, from the 17^th century to the last decades of the 19^th; the third is the one we are living in now.

During the second of these epochs, a seesawing occurred that displaced time’s center of gravity. Previously it was located in the distant past and now it was relocated in the future. In other words, the time dominated by the past – the seat of models, examples, norms that men were obliged to follow, was replaced by time oriented towards the future, one that people were now obliged to build. This seesawing of time between the passéist and the futurocentric is particularly manifest in the slow marginalization of religion by science and ideologies; both exert a growing influence on the behavior of individuals and societies, on economies, on politics. The problem of relations between qualitative and quantitative time comes in addition to the problem of relations between religion on the one hand and science and ideology on the other, between the past and the future.

During the first of the three epochs, we are dealing with a cyclical and stable movement of stars and, on the opposite pole, with linear and irreversible changes that characterize life, in particular human life; in between are located meteors. The stability of the cyclical movement of stars cannot be explained other than through the action of an agency external to visible world. This agency makes the visible world the cosmos, because it creates time as a coordination of all movements and all changes. But it itself resides outside time, in eternity. The problems of chronosophy, reduced to their simplest form, are therefore those of the relations between linearity, cycle, and eternity, between the time of man, the time of nature, and the time of God. These problems are discussed by Plato and Aristotle, and by St Augustine. According to Aristotle, the action of the Prime Mover influences visible movements and changes through the sphere of fixed stars, while Augustine places the question of time in the invisible realm, between God and the soul which aspires towards eternity, even if it is obvious for him that it is God who created the visible world and who maintains its existence.

When philosophy turned towards quantitative time, God became the great watchmaker. For Newton, time is a universal frame, uniform and empty, with a direction and a speed, in relation to which may be determined the directions and speeds of all movements and all changes (actually, Newton’s theory was more complex). But for Leibniz, such a time is unintelligible. For him, time is an order of succession inherent to created beings, to monads, because it is created with them and built into the changes of each one. A unique clock in the hand of God or a plurality of clocks regulated by Him once and for all? This question is at the center of the controversy between Newtonians and Leibniz. The controversy focuses therefore around relations between quantitative and qualitative time, which would become central to future debate on the subject. But first, time would be disconnected from God via its reduction by Hume to a psychic time and its identification by Kant with one of two transcendental forms of sensibility, the second being space. For both, time is human time, even if for Kant the human being is only a peculiar case of a transcendental subject of knowledge. I cannot enter here into the difficulties with which Newtonian time, the same as that of Kant, was confronted in the physics and philosophy of the late 19^th century. Suffice to say that quantitative time is henceforth identified with the mechanical time imposed by clocks on all social existence and therefore opposed to organic time, qualitative time, the time of nature, the time of life. This conflict traces the principal dividing line in the philosophy of time in the 20^th century. It plays out between, on the one side, Bergson, Husserl, and Heidegger, who, whatever the differences between their positions, all favor the time of the consciousness or Dasein, i.e. qualitative time, and, on the other side, Poincaré, Einstein, and Reichenbach, for whom there is only physical, quantitative time, whose properties are those of the clocks.

It follows that opinions about time are varied because the time itself has a history. Hence, thinkers who follow one another do not necessarily speak about the same time. But opinions are also varied among contemporaries, since some focus on nature and others on soul, some see the time of clocks negatively and that of consciousness positively, while others make an opposite assessment. The plurality of opinions about time is a consequence of the plurality and heterogeneity of time itself.

 

Krzysztof Pomian is Professor of History at the Nicolaus Copernicus University (Torun) and Academic Director of the Museum of Europe in Brussels.

* This paper is based on a lecture given at the IWM on April 18, 2013.