Early Modern Philosophy

Sir Isaac Newton & Gottfried Leibniz
Two opposing philosophical positions on time in the Early Modern period were championed by Sir Isaac Newton and Gottfried Leibniz

After a long lull, the nature of time once again became a point of philosophical contention during the 17th and 18th Century, the so-called Age of Enlightenment or Age of Reason.

René Descartes took the rather mystical view that, although a material body has the property of spatial extension, it has no inherent capacity for temporal endurance. Rather, God, by his continual action, sustains (or effectively re-creates) the body at each successive instant. Time is therefore a kind of constant process of re-creation by God.

Realism and Anti-Realism

But the two main conflicting schools of thought on the subject during this period are sometimes characterized as realism vs. anti-realism or absolute vs. relational.

The realist viewpoint, championed by Sir Isaac Newton and his fellow Englishmen Isaac Barrow and  Samuel Clarke, asserted that time is part of the fundamental structure of the universe, and that it can best be looked on as a dimension in which events occur in sequence (indeed, this view is sometimes referred to as “Newtonian time”). According to Newton, absolute time exists independently of any perceiver, progresses at a consistent pace throughout the universe, is imperceptible, and can only be understood mathematically. Time is therefore an entity in its own right, and we (and all the objects in the universe) are just temporarily “occupying” it. However, as mere humans, Newton cautioned, we are only capable of perceiving what he called relative time, which is a measurement of perceivable objects in motion (like the Moon or Sun), from which we infer the passage of time.

On the other hand, Newton’s great rival Gottfried Leibniz firmly believed that time does NOT refer to any actual existing dimension that “flows” and that events and objects move through in some way. Rather, the anti-realist view of time claims that it is merely a convenient intellectual concept (like space and number) that enables us to sequence and compare events. Thus, time ceases to have any meaning unless there are objects with which it can interact or relate to (for this reason, this view is also known as relational time), so that, in a very real sense, the events taking place actually ARE time. Certainly, time does seem to be a very abstract concept: if we try to think of a moment in time, all we can really do is think of an event that happened at that moment; we cannot point to, or even describe, the moment itself. According to this view, then, time (and space) are merely the product of the way we represent things to ourselves, because we are only capable of knowing objects and events as they appear to us. During the years 1715-6, Leibniz and Clarke carried on an extensive public correspondence, arguing over the (respectively) relational or absolute qualities of time and space.

Another great German philosopher, Immanuel Kant, in his influential 1788 book The Critique of Pure Reason, described space and time as a priori notions that are necessary to allow us to comprehend sense experiences, but not substances or entities in themselves (in his terminology, “phenomenally real” but “noumenally unreal”). He believed that our minds actually structure our perceptions in such a way that space always has a Euclidean geometry, and time always has the linear structure of a mathematical line. Time is therefore merely one element of the systematic framework we use to structure our experience, the one we use to quantitatively compare the interval between, or the duration of, events. So, although empirically real (i.e. not a mere illusion), Kant asserted that time is “transcendentally ideal”.

Although a physicist, Ernst Mach was also relativist in the mold of Leibniz. Writing towards the end of the 19th Century, Mach argued that, even if it was not obvious what time and space were relative to, they were still relative to the “fixed stars” (i.e. the bulk of matter in the universe) if nothing else, and that in an empty universe such concepts would no longer have any meaning.

Specious Present
William James
The philosophical idea of the specious present was promoted by William James

Historically, the present has usually been considered a momentary, instantaneous, even unmeasurable, time. In the late 19th century, though, E. Robert Kelley (writing under the pseudonym E.R. Clay) started to contest that notion, introducing the concept of the “specious present”. Kelley saw the present as merely the most recent part of the past. The early psychologist and philosopher William James, further developed the idea, describing the specious present as “the short duration of which we are immediately and incessantly sensible”.

James argued that whatever we experience, however fleeting, always has an element of an earlier part and a later part, and anything with an earlier part and a later part cannot possibly be instantaneous in physical time. Another way to look at this is that what an observer sees at any one time is some kind of motion, and motion takes place over an interval, so therefore what the observer sees as present actually occurs over an interval. If a sequence of events occurs over a short enough duration of physical time, we may experience them as simultaneous in perceived or psychological time, but they nevertheless still take place over a short period of physical time.

It seems, then, that, at least to some extent, we perceive events as present that are actually past. In fact, given the fact that the speed of both sound and light are finite, and given that some additional time is needed for the transmission of information from our sense receptors to our brain, it seems that we can only ever perceive what is past. Some proponents of the specious present have gone into even finer arguments over whether or not individual specious presents can overlap each other, and about how they combine to form our stream of consciousness.

Conventionalism

Our everyday use of time relies to a large extent on conventionality. For example, it is a more or less arbitrary convention or convenience that we agree to the practice of re-setting our clock by one hour as we cross a time-zone, that there are twenty-four hours in a day rather than ten, and sixty seconds in a minute rather than twelve, that we measure our dates from the putative date of the birth of a particular religious figure, etc.

The 19th Century French physicist, mathematician and philosopher Henri Poincaré was a great believer that convention plays an important role in physics, and in particular that the geometry of space and time is largely decided by convention, since different geometries may describe a set of objects equally well. This position, referred to as conventionalism, was later taken up by the philosopher of science, Hans Reichenbach, who argued that the whole edifice of relativity (see the section on Relativistic Time) rests on what is effectively a convention, namely that the speed of light is a constant, albeit a convention backed up by the equations of James Clerk Maxwell, and the practical experimentation of the famous Michelson-Morley experiments.

Phenomenology

In the late 19th and early 20th Century, the German philosopher Edmund Husserl, founder of the influential phenomenology movement, began to consider time and our internal consciousness of time. He asserted that we cannot have any perception of the immediate present without some memory of the past and some expectation of the future to give it context.

The French phenomenologist and intuitionist philosopher Henri Bergson formulated a view of time that was neither a real homogeneous medium nor a mental construct, but possesses what he referred to as “duration”. He saw the apparently fluid flow of time as actually composed of a myriad tiny temporal particles, which are pieced together by our consciousness. Noting that as soon as one tries to measure a moment it is gone, and that the passage of time is subjective for different individuals in different circumstances, Bergson concluded that duration (or time) can only be shown indirectly and incompletely, and can only be grasped through a simple intuition of the imagination. Bergson thought of time as something entirely derived from subjective experience, so that babies would not experience time directly (as Kant believed), but rather would have to learn how to experience it. He even went so far as to claim that the modern scientific concept of time as a dimension (see the section on Relativistic Time) actually misrepresents reality.

In his complex but important 1927 book Being and Time, the German phenomenologist and existentialist Martin Heidegger concluded that, we do not exist WITHIN time, but in a very real way we ARE time, and the whole concept of time is inseparable from the human experience. Also, he noted that, because we can allow the past to exist in the present through memory, and even allow a potential future occurrence to exist in the present due to our human propensity to care and be concerned about things, then we are not stuck in simple sequential or linear time, but can step out of it almost at will.

>> Modern Philosophy

Modern Philosophy

J.M.E. McTaggart
Much of the modern philosophical debate on time was triggered by work by J.M.E. McTaggart

In the 20th Century, the philosophical debate on the nature of time continued unabated, given new impetus by the work of the British idealist philosopher J.M.E. McTaggart, particularly his 1908 paper, The Unreality of Time.

McTaggart argued that time is actually unreal because our descriptions of it are necessarily either contradictory, circular or insufficient. McTaggart pointed out that we see the present moment we are living through as the ONLY present time. But, all other moments, past and future, also either were or will be the present time at some point or other, so how can this contradiction be reconciled? McTaggart’s detailed analysis subsequently led to a number of productive areas in the modern philosophy of time, including the tensed and tenseless theories of the passage of time.

Tenseless and Tensed Theories of Time

The tenseless theory of time (also known as the B-theory, based on McTaggart’s B-series method of ordering events) calls for the elimination of all talk of past, present and future in favour of a tenseless ordering of events using only phrases like “earlier than” or “later than”. The argument behind this is that tensed terminology can be adequately replaced with tenseless terminology, e.g. the future-tensed sentence, “we will win the game” can be adequately expressed as, “we do win the game at time t, where time t happens after the time of this utterance”. The future tense has therefore been removed, and the verb phrases “do win” and “happens after” are logically tenseless, even if they are grammatically in the present tense. If this is true, then there is no essential difference between the past, present, and future, all of which are therefore equally real (see the section on Eternalism below), and the passage of time must be merely an illusion of human consciousness.

The tensed theory of time (the A-theory), on the other hand, denies that such an argument is valid, and argues that our language has tensed verbs for a good reason, because the past, present and future are very different in quality. The A-theory therefore denies that the past, present and future are equally real, and maintains that the future is not fixed and determinate like the past. A-theorists believe that our ordinary everyday impression of the world as tensed reflects the world as it really is: the passage of time is an objective fact.

Presentism and Eternalism

The philosophy of time that takes the view that only the present is real is called presentism, while the view that all points in time are equally “real” is referred to as eternalism.

Thus, according to presentism, only present objects and present experiences can be said to truly exist, and things come into existence and then drop out of existence. Therefore, past events or entities, like the Battle of Waterloo or Alexander the Great, literally do not exist for presentists, and, because the future is indeterminate or merely potential, it cannot be said to exist either.

Eternalism, on the other hand, holds that such past events DO exist, even if we cannot immediately experience them, and that future events that we have not yet experienced also exist in a very real way. For eternalists, the “flow of time” we experience is therefore  just an illusion of consciousness, because in reality time always everywhere. Eternalism takes inspiration to some extent from the way time is modeled as a fourth dimension in the theory of relativity of modern physics (see the section on Relativistic Time), so that future events are “already there” but just have not been encountered yet, and the past literally still exists “back there” in the same way as a city still exists after we drive away from it. This is often referred to as the block universe theory or view because it describes space-time as an unchanging four-dimensional “block”, rather than three-dimensional space modulated by the passage of time.

There is also a variation of eternalism, sometimes known as the growing block universe theory of time or the growing block view, in which more and more of the world comes into being with the passage of time (hence, the block universe is said to be growing), so that the past and present clearly do exist, but the future is not yet part of this universe and therefore does not exist. This in some ways gels with our intuitive impression that the past (which is fixed, and can be accessed through remembering and physical records) is very different in nature from the future (which is variable, uncertain and cannot be accessed or consulted).

Endurantism and Perdurantism

A similar but separate dichotomy exists with regard to the persistence of objects through time. Endurantism is the more mainstream or conventional view, asserting that, when an object continues to exist through time, it exists completely at different times, with each instance of its existence fundamentally separate from the other previous and future instances. Perdurantism, on the other hand, holds that something that continues to exist through time exists as a single continuous reality, and the thing as a whole is then the sum of all of its “temporal parts” or instances of existing (the temporal parts of a particular person, for example, include their childhood, middle age, old age, etc).

This argument goes back to ancient Greece and Heraclitus’ contention that we can never step into the same river twice (because the water is not the same water the second time around). An endurantist would tend to agree with Heraclitus, even though our common sense tells us that the river at one time and the river at another time are in fact the same river, and nothing about it has essentially changed. A perdurantist, on the other hand, would argue that it is possible to step into the same river twice by stepping into two different temporal parts of it.

Typically, presentists are also endurantists, and eternalists are perdurantists, although this is not necessarily the case.

New Philosophical Ideas from Modern Physics

 

The Many Worlds Theory of parallel universes is one of several philosophical approaches to time prompted by new ideas in modern physics
The Many Worlds Theory of parallel universes is one of several philosophical approaches to time prompted by new ideas in modern physics

The concept of alternative universes and the many-worlds interpretation of quantum mechanics (see the section on Quantum Time), which is gaining increasing attention in the world of modern physics, adds a whole new dimension to the discussion of the nature of time. In the disconnected time streams in a potentially infinite number of parallel universes, some could be linear and others circular; time could continuously branch and bifurcate, or different time streams could even merge and fuse into one; the laws of causality and succession could break down or just not apply; etc, etc.

Although modern physicists generally believe that time is just as “real” as space (see the section on the Physics of Time), a few mavericks, such as Julian Barbour, have tried to show scientifically that time exists merely as an illusion. In his 1999 book The End of Time, Barbour makes the argument that the quantum equations of the universe only take their true form when expressed in a timeless realm that contains every possible “now” or momentary configuration of the universe, a realm Barbour called “platonia”. Barbour argues that, in order to reconcile general relativity with quantum mechanics, either time does not exist, or else it is not fundamental in nature.

The possibility that time might have more than one dimension has occasionally been discussed both in physics and in modern analytic philosophy. The English philosopher and scientist John G. Bennett has posited a six-dimensional universe, with the usual three spatial dimensions and three time-like dimensions, which he called time (the sequential chronological time that we are familiar with), eternity (cosmological time or timeless time), and hyparxis (characterized by Bennett as an “ableness-to-be”, and may be more noticeable in the realm of quantum processes).

Imaginary time is a concept derived from quantum mechanics. Stephen Hawking introduced the concept in his 1988 book A Brief History of Time as a way of avoiding the idea of a singularity at the beginning of the universe, where time suddenly starts and all the laws of physics break down. Hawking proposed that space and imaginary time together are finite in extent but with no boundary (in a similar way as the two-dimensional surface of a sphere has no boundary). Imaginary time is not imaginary in the sense that it is unreal or made-up, but it is admittedly rather difficult to visualize. It is perhaps easiest to think of as a line perpendicular to the past-future line of regular or “real” time, in much the same way as the imaginary numbers run perpendicular to the real numbers in the complex plane in mathematics. Under this model, “real time” as we know it would still have a beginning, but the way the universe started out at the Big Bang would essentially be determined by its state in imaginary time. The beginning of the universe would then be a single point, analogous to the North Pole of the Earth, but not a singularity.

 

Ancient Philosophy

Kalachakra, the Wheel of Time
Kalachakra, the Wheel of Time, is a representation of the cyclic view of time in some ancient philosophies

Since the earliest days of philosophy in ancient India and Greece, the true nature of time has exercised some the greatest minds in history.

Mythology

In ancient times, mythology and other traditional narratives were used to try and make sense of the universe we find ourselves in.

In Greek mythology, Khronos (or Chronus to the Romans) was the personification of time, not to be confused with Cronus, the Titan and father of Zeus. The Greeks had two different words for time: chronos refers to numeric or chronological time, while another word kairos refers to the more qualitative concept of the right or opportune moment. The figure of Khronos was typically portrayed as a wise old man with a long grey beard, similar to the later European folklore image of Old Father Time, although he was originally described in very early Greek mythological tales as serpentine in form, with three heads, of a man, a bull and a lion. A separate figure, Geras, was the Greek god of old age, usually depicted as a tiny shrivelled-up old man. The Horae or Hours were the goddesses of the seasons and the natural flow of time, generally portrayed as personifications of nature in its different seasonal aspects, and with the cycle of the seasons themselves symbolically described as the dance of the Horae.

Other mythologies had their own time-related gods, such as Heh the Egyptian deification of eternity or infinity, Zurvan the Zoroastrian god of infinite time (and the father of the twin spirits of good and evil), Elli the Norse god of old age, etc.

Wheel of Time

In ancient Indian philosophy, as expounded in early texts such as the Vedas of the late 2nd millennium BCE, the universe goes through repeated cycles of creation, destruction and rebirth (with each cycle lasting 4,320 million years according to some sources). This led to a cyclic view of time, the so-called “wheel of time” or Kalachakra, in which there are repeating ages over the infinite life of the universe. This was coupled with a belief in an endlessly repeated cycle of rebirths and reincarnations for individuals. The wheel of time concept is found in Hinduism and Buddhism, as well as in the beliefs of the ancient Greek Orphics and Pythagoreans, but also in other disparate religions and beliefs such those of the Maya, the Q’ero Indians of Peru and the Hopi Indians of Arizona.

The idea of time as consisting of endlessly repeated cycles is perhaps an unsurprising one given the observed repetitiveness of other natural phenomena, such as the day-and-night cycle, the motion of the tides, the monthly cycle of the Moon, the annual cycle of the seasons, etc. It does, however, seems to presuppose an overall linear ordering in some sort of “hypertime” of all the cycles, so that each cycle can be distinguished from its predecessors and successors because it occurs at a different point in hypertime.

Ancient Greece

The early Greek philosophers generally believed that the universe (and therefore time itself) was infinite with no beginning and no end. In the 5th Century BCE, the Sophist philosopher Antiphon asserted that time is not a reality (hypostasis), but a concept (noêma) or a measure (metron). Also in the 5th Century BCE, Parmenides saw time (as well as motion and many other everyday things that we take for granted) as nothing more than an illusion because, he argued, all change is impossible and illusory (time as an illusion is also a common theme in Buddhist thought). Parmenides, then, believed that reality was limited to what exists in the here and now, and the past and future are unreal and imaginary. His near-contemporary Heraclitus, on the other hand, firmly believed that the flow of time is real and the very essence of reality.

Zeno’s Paradoxes were devised at least partially to support Parmenides’ doctrine that change and plurality and the passage of time are merely illusory and lead to paradoxes and absurdity. In the best known of these, Achilles and the Tortoise, Achilles allows the tortoise a head start of, say, 100 metres in a footrace. After some finite time, Achilles will have run 100 metres, bringing him to the tortoise’s starting point, but during this time the slower tortoise has run a much shorter distance, say, 10 metres. It will then take Achilles some further time to run that distance, by which time the tortoise will have advanced yet further, etc, etc, so that whenever Achilles reaches somewhere the tortoise has been, he still has further to go. Because there are an infinite number of points Achilles must reach where the tortoise has already been, Zeno argues that he can never overtake the tortoise, and the tortoise must win the race. Indeed, another corollary of this paradox is that neither Achilles nor the tortoise can ever actually finish the race, as they are constantly having to cover an ever smaller distance, ad infinitum, and, as Zeno averred, “it is impossible to traverse an infinite number of things in a finite time”.

Plato, in the 4th Century BCE, believed that time was created by the Creator at the same instant as the heavens. But in an attempt to slightly be more scientific, Plato identified time with the period of motion of the heavenly bodies. Plata was also aware of the so-called “Great Year”, a complete cycle of the equinoxes around the ecliptic (effectively the return of the planets and the “fixed stars” to their original relative positions, a process that takes about 25,800 years). The Pythagoreans and some Stoic philosophers like Chrysippus saw the end of this cycle as the end of time iself, after which history would start to repeat itself all over again in an endless repetition.

Plato’s student Aristotle saw time as an attribute of movement, as something that does not exist on its own but is relative to the motions of things. He called time “the numeration of continuous movement” or “the number of change in respect of before and after”. Aristotle argued that time is essentially a measurement of change, and therefore cannot exist without some kind of succession or change, and also that it requires the presence of a soul capable of “numbering” the movement. Although he saw time as the measure of change, he stressed that it was not the same thing as change, because a change may occur faster or slower. Aristotle also believed that, although space was finite (with only some undefined void existing beyond the outermost sphere of the heavens), time was infinite, and that the universe has always existed and will always exist. Furthermore, he believed that time was continuous, not discrete or atomistic, in the same way as a line can be divided and sub-divided ad infinitum.

Aristotle was also the first to frame a commonly-mentioned paradox about the existence of time, recapitulated by St. Augustine several centuries later: if time essentially consists of two different kinds of non-existence (the past or the “no longer”, and the future or the “not yet”) separated by a nothing (the instantaneous and vanishing present or “now”), how then can we talk of time as actually existing at all?

The Dark Ages

Mithraism, a mystery religion influenced by ancient Zoroastrianism, and a strong competitor to Christianity in the early years CE, believed in a finite “Time of the Long Dimension” which repeated itself in cycles of 12,000 years, within the overall container of infinite time. In general terms, Zoroastrianism saw the world around us as a kind of battlefield between a bad god and a good one, and saw time as the duration of this battle.

The early Christian theologian St. Augustine (4th – 5th Century CE) probably thought more deeply about the nature of time than any philosopher since the ancient Greeks, but his deep thoughts remained inconclusive. Echoing the earlier comments of the Neo-Platonist Plotinus, St. Augustine famously encapsulated the experience of so many of us, when he observed: “What then is time? If no one asks me, I know; if I wish to explain it to one that asks, I know not”. He was only able to conclude that time was some kind of a “distention” of the mind which allows us to simultaneously grasp the past in memory, the present by attention, and the future by expectation. St. Augustine also adopted a subjective view of time, that time is nothing in reality but exists only in the mind’s apprehension of reality.

Middle Ages
Sistine Chapel, Rome
In the Middle Ages, Christian philosophers had to reconcile the concept of time with the creation of the universe by God

Christian and Muslim philosophers tried their best to incorporate the ideas of Aristotle into their theology during the early Middle Ages, but they struggled mightily with his belief that time was infinite. Perhaps the first Christian writer to put forward a solid argument against the ancient Greek notion of an infinite past was the Alexandrian philosopher John Philoponus in the 6th Century. The doctrine was further developed and institutionalized by the Christian scholastics of the 11th-13th Century, including Thomas Aquinas and St. Bonaventure, as well as Muslim philosophers such as Al-Kindi and Al-Ghazali, and the Jewish philosophers Maimonides and Saadia Gaon.

Christianity and the other Abrahamic faiths, Islam and Judaism, believed in an all-powerful and infinite God (in contradistinction to everything else, which was therefore finite), and so medieval Christian, Muslim and Jewish philosophers and theologians developed the concept of the universe having a finite past with a definite beginning (the moment of its creation by God). Time, therefore, was necessarily finite in nature, a doctrine known as temporal finitism. The general Christian view is that time will come to a definite end with the end of the world, in the so-called “end-times” and the cataclysm of the Apocalypse.

The 13th Century Italian theologian Thomas Aquinas objected to Aristotle’s assumption of infinite time on the grounds that, although the universe could in theory have existed infinitely into the past, in fact it did not (it began with God’s creation of the Earth a finite time ago), warning that our imagination cannot always be trusted to tell us how things really are. The 13th Century philosophers Henry of Ghent and Giles of Rome made the rather fine distinction that the continuum of time does actually exist in reality and not just as a mind-dependent concept, but that it can only be distinguished into earlier and later parts by the mind.

Various versions of Christian creationism persist to this day, although not all are quite as literal as that of the medieval philosophers, or of the 17th Century bishop James Ussher, who famously concluded in the that the Earth was created by God on Sunday, 23rd October 4004BCE, at precisely 6pm! Young-Earth creationists still believe that God created the Earth, sometime within the last ten thousand years or so, over a period of 6 days, literally as described in the Genesis creation narrative. Others have even specified that He deliberately created it with the appearance of age, complete with fossils, rock strata, etc. Old-Earth creationists, on then other hand, have attempted to update their beliefs to take account of the scientifically proven age of the Earth (around 4.6 billion years) by claiming that the six days of creation in Genesis were not ordinary 24-hour days, but “God-days”, which may be the equivalent of millions or billions of years of human time. Still others claim that life was created relatively recently by God, but on a pre-existing old Earth.

In the 14th Century, the French mathematician Nicole Oresme was perhaps the first to try and put the study of time on a mathematical and scientific basis. He asked the question as to whether the celestial motions of the Sun, Moon and planets are commensurable, and so whether there is a “basic” time interval of which the day, month and year are all exact integer multiples. Oresme suggested that a creator of the universe might well have arranged things so, but his conclusion was that that no two celestial motions are actually commensurable, and so there is no such basic time interval.

>> Early Modern Philosophy

Philosophy of Time

Aristotle
Philosophers have been grappling with the nature of time since the time of Aristotle and even before

All animals except humans live in a continual present, with no sense of the temporal distinctions of past, present and future. Our consciousness of time is therefore one of the most important distinguishing features of humankind, and one of the things that truly separates us from the lower animals. It comes as no surprise, then, that from time immemorial, philosophers, teachers and theologians have speculated on the true nature of time. Does time have a substance and, if so, what is it made of? How do we know that time really exists? Does time have a beginning and an end? Is it a straight line or a circle?

There is general agreement among philosophers that time is continuous (i.e. we do not experience it as stopping and starting, or darting about at random), and that it has an intrinsic direction or order (i.e. we all agree that events progress from past to present to future). There is also a more or less general agreement that is it objective, and not subjective or dependent on its being consciously experienced, which is borne out by the almost universal agreement on the time order of so many events, both psychological and physical, and the fact that so many different physical processes bear consistent time relations to each other (e.g. the rotation of the Earth, the frequency of oscillation of a pendulum, etc). However, even given that, many differing opinions and approaches to what time actually is have been put forward over the centuries.

The ancient philosophy of India and Greece was among the first to confront and question the real nature of many things that had been taken for granted (e.g. matter, space, nature, change, etc), and time was one of the many mysterious concepts they argued about at length. One major point of contention among the ancients was whether time is linear or cyclical, and whether it is endless or finite. (“Ancient philosophy”, for these purposes, is taken to include philosophical thought up to the late Middle Ages.)

During the Age of Enlightenment of the 17th and 18th Century, early modern philosophy began once again to consider questions of whether time is real and absolute or merely an abstract intellectual concept that humans use to sequence and compare events. In the 19th Century, philosophers began to question whether the present was really an instantaneous concept or a duration, and the conventionalists and phenomenologists all made their own contributions to the debate on time.

More recently, modern philosophy has continued to argue over whether time is real or “unreal”. But a whole host of other philosophical issues related to time have also surfaced, including whether time is tensed or tenseless, whether the present is instantaneous or a duration, whether the past and the future can be said to really exist, the manner in which objects persist though time, etc. Some of the novel ideas from modern physics have also generated new philosophical insights and hypotheses concerning the nature of time.

>> Ancient Philosophy