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Do the past and future exist?
One common agreement among many who think about time, is that time, if it involves the mind, is, in some meaningful sense, fundamentally mind-dependent. Arguably, every question about time is reducible to this single, dichotomous split: whatever time is, and whatever it is like, is it mind-dependent, or is it independent? To begin, then, we will seek to resolve this fundamental question; we will ask two great philosophers their opinion of time, and whether it is mind-bound, or whether, outside of man, time has a life of its own.
Consider Immanuel Kant. Kant, an acolyte of David Hume, said, in the preface of his Prolegomena to Any Future Metaphysics, a summary of his major work, Critique of Pure Reason, that his teacher had awaken him from a period of “dogmatic slumber”. By this, Kant meant that Hume, who questioned the claim that a priori truths exist, forced him to refocus his philosophical concerns, away from pure reason independent of all experience, towards an epistemology that favoured empirical verification. The central focus of the Critique was whether or not time had a beginning (Popper 2002, 241). On thinking a while Kant found, to his regret, that he could produce equally satisfactory proofs for both possibilities. For Kant, these contradictions had profound implications. The two proofs are as follows.
1st Proof: Kant begins by proposing an infinite sequence of years (or days, or hours, or any equal and finite partition of time). An infinite sequence does not have an end; an infinite sequence can never be completed; by definition, only finite things have identifiable boundaries: a completed infinite sequence is a contradiction in terms. Kant reasons simply, that, if time is infinite, an infinity of time has elapsed, or been completed, from the vantage point of the present moment. This moment is presumably different from all others, and is, in some sense, being unique, defined by finitude. Thus, if time exists, it has an end: now. This contradicts the idea that an infinite sequence can never be completed. Therefore, time must have a beginning. This concludes the first proof. [However, note Nick Bostrom in his paper Infinite Ethics: “In standard cardinal arithmetic, any infinite quantity is unchanged by the addition or subtraction of any finite quantity” (2011, 1). This would suggest that the completion of finite periods of time does not contradict the concept of an infinite series, a suggestion which, essentially, is a refutation of Kant’s 1st proof].
2nd Proof: Next, Kant considers a time before time, that which he supposes must have existed before the world came into being. In this timeless age, there can be no finite partitions of time; no time intervals are differentiated one from another by the relation of them to each other or to things or events, because before time no things or events even exist. Now, take the very beginning of time, and consider the moment immediately before it. Clearly, this moment is unique from all others, due to its relationship to time’s inception—but this is a contradiction, for, before time, there can be no unique temporal thing, a thing simultaneously empty of temporal meaning, but which gains temporal meaning by its relation to the beginning of time. Kant refutes the finitude of time by claiming that before time there must have been a unique temporal thing, defined by its unique relation to the beginning—that before time, there must be time—which is impossible.
On the basis of these antinomies, Kant concluded that the existence of time is a logical contradiction and that it does not exist. It exists only as a mental idea: we order things in the world with appeals to time, much as we order music according to genre, or files by placing them in their own compartments. Time is neither a thing nor an event: it cannot be observed; we cannot support its existence through observation, much less through logic. Rather, time is merely a way of seeing the world—we wear “time-coloured glasses”—it is an instrument of measurement: whenever we observe things in the world, we immediately and intuitively arrange them in terms of their placement in time. Thus time is an intuition, a frame of reference that structures our experience but is not a part of it. This is why we run into all sorts of trouble when we try to talk about time as though it actually existed; this is why the proofs, each of which spoke about time as an actual thing, ran into insoluble contradictions: because time does not exist.
Kant’s Critique of Pure Reason attacked “armchair reasoning”, that did not allow empirical evidence to validate or falsify its claims. Ironically, the rejection of the antinomies of time rested on the conjunction of two logical fallacies. In critiquing pure reason, Kant used reason only. Kant, from his study, did not concern himself with the immediate present; and in his neglect, he forfeited that which all who exist, know with a visceral certainty to be true: that in this moment I exist, and in the next moment I do as well. I know that time exists with the same certainty that I know any other fact about my existence, such as that my hand, in front of my face, is external to my mind. Do we have reason to question this most basic of experiences?
In Book XI of his autobiographical Confessions, Saint Augustine of Hippo enters on a long and fascinating exploration of time, in the course of which he raises this conundrum: what is it actually that passes when we speak of the flow of time? He reasons as follows:
But we measure times as they are passing, by perceiving them; but past, which now are not, or the future, which are not yet, who can measure? unless a man shall presume to say, that can be measured, which is not. When then time is passing, it may be perceived and measured; but when it is past, it cannot, because it is not” (1983, 11.16.21).
“Who will tell me that there are not three times . . . past, present, and future; but present only, because those two are not? Or are they also; and when from future it becometh present, doth it come out of some secret place; and so, when retiring, from present it becometh past? For where did they, who foretold things to come, see them, if as yet they be not? For that which is not, cannot be seen. And they who relate things past, could not relate them, if in mind they did not discern them, and if they were not, they could no way be discerned. Things then past and to come, are” (1983, 11.17.22).
Augustine believes, that that thing we measure, when we measure time—that it cannot be the past, as it has ceased to be, and what no longer exists, cannot be said to have properties that persist, such that can be measured. Neither can it be the present, for, aside from the problem of assessing the duration of a thing that is still ongoing, the present, being continuous—being neither past nor future, but ongoing, and having no measurable length—the present does not have duration. That is, the present is eternal, and the past and the future do not exist.
Augustine further defends this radical presentism by suggesting that what is measured when we measure past time intervals is a bit of memory, from which he concludes that time is mind-dependent, and, thus, that the direct object of mental experience—the present—is all that can be said with any confidence to exist. According to Augustine, everything that is perceived is perceived right now. It is impossible to perceive the past—unless the past were perceived now, at which time it would become the present; or unless we perceive it through memory, which, again, is perceived now. Note that this mind-dependency needn’t be the case; it may be true that time is mind-independent, a thing which is experienced by a cognizant being in its own present moment; however, it is difficult to show that a thing which relies on its mind for all experience can prove that an object of its experience is mind-independent.
Since the time of Kant, the physical sciences have attempted many times to quantify time. Unfortunately, attempts to quantify, through empirical measurement, the nature or the mechanics of time, have failed. This failure can be explained in one of two ways: first, that the instruments used to observe time were sub-prime or insufficient; second, that time does not exist to be measured. According to Kant, and, in a sense, to Augustine, time is imperceptible, and thus cannot be measured (alternately, one could be a new mysterian about time, and state that, though it exists, it cannot be humanly measured; however, in reply, if time is immune to measurement, what reason have we to assume it exists?). Since we do not experience time with any of our five senses, it sounds strange to say we touch time, or see it or hear it as it passes—and claims of “imperceptibility” gain weight. And when, deprived of our senses, we notice the passing of time in our procession of thoughts, this experience of time would suggest to us, either, that time is a mental illusion, or that there is an additional “sixth sense”, hitherto unknown to us, with which time and the mind are perceived. The following will examine these possibilities.
The metaphysics of time frequently concerns itself with whether time exists in a tensed fashion as past, present, and future, or whether there is no privileged position in time, and all that can be said of time is that it moves in an ordered series. Those who hold the former position, that time is tensed, are called A-theorists; those who hold the latter view, that time is tenseless, are B-theorists. This terminology comes from the work of McTaggart (1908), who stated that there are two theoretical ways we can conceptualise time: as an A-series, as an objective thing-in-the-world, whose passage from past to future, which we experience, is real; and as a B-series, in which events are regarded as occurring earlier than, later than, or simultaneous with, other events, but does not allow the objective ontological privileging of moments into past, present and future.
For reasons already explained, and for reasons to come, discussion of A-theory will be overlooked. We will focus on tenseless B-theory. B-theorists argue that what makes statements such as, “it is cold now” and “it happened hours ago”, true, is not that they refer to truths about pastness, presentness, or futurity, but, rather, that they refer to tenseless and subjective facts concerning precedence and simultaneity. For example, I form the belief “it is cold now” at the very same moment that it is cold, making it simultaneous, and, therefore, valid. This favour for subjective assessments of tense will be important in the coming discussion of relativity theory.
Concerning B-theory: when we assume a temporal relationship between a past and a present phenomena—for example, a thunderclap (B) proceeding a lightning strike (A)—we do not perceive the two events occurring simultaneously. Simultaneity precludes succession. If two events occur one after the other, they are not simultaneous; if one event happens after another, they did not happen at the same time. So, in order to establish a relationship of temporal succession between events A and B, we must assume that A is not perceived when B is perceived. This means that, strictly speaking, we perceive A and B at different times, not together. Because A and B do not occur simultaneously, we call them separate events. On the nature of events, McTaggart said the following:
It would, I suppose, be universally admitted that time involves change . . . What is it that changes? . . . [In a B-series] N will always have a position in a time series, and has always had one. That is, it will always be, and has always been, an event, and cannot begin or cease to be an event . . . or shall we say that one event M merges itself into another event N . . . If therefore M changes into N at a certain moment, then, at that moment, M has ceased to be M, and N has begun to be N. But we have seen that no event can cease to be, or begin to be, itself, since it never ceases to have a place as itself in the B series. Thus one event cannot change into another (1908, 459-460).
And so on. In this way, McTaggart argues that time involves change; that, in a B-series, change is impossible; and that B-theory, having no change, has no time. In what remains of this essay, evidence will be offered that change is not necessary for time to exist (because all moments exist simultaneously and timelessly in a “block universe” where the need for change becomes redundant); that the idea that time moves linearly is questionable; and that there is no objective world in which one event can be absolutely determined to have caused another, throwing into disarray the entire notion of causation.
Concerns about tense and timelessness continue to vex metaphysicians and cosmologists; however, in modern times, the baton of inquiry has been taken up most fervently by the cosmologists. It was only in the 19th and 20th centuries that the scientific method was brought to bear on the previously purely rational search for time. According to Karl Popper, the second law of thermodynamics (2nd law), or the law of entropy increase, when supported by a small number of technical and mathematical additions, proves that time is eternal (2001, 183). In addition, the philosophical implications of the special theory of relativity (SR) support a position known as “eternalism”, the contrary position to presentism. The following will determine the compatibility of presentism and eternalism under the assumptions of SR and the 2nd law.
Eternalism speaks equally of the metaphysics and the ontology of time. That is, eternalists propose that past, present and future all co-exist, that they exist at the same time. In consequence, the simultaneity of all times gives none a privileged ontological position over another, a similar position to the one held by B-theorists. The claim, such that Augustine makes, that only the present exists, because the past and future to do not exist to be perceived, is compatible with eternalism, if, and only if, it is acknowledged, as the eternalists acknowledge, that the “presentist feeling” is illusory. If the claim to presentism is explained to be no more than a description of phenomenological experience, not a defence of metaphysical reality, then presentism and eternalism can be made crudely compatible. Yet, under different assumptions, namely, those of SR, all pretence to presentism breaks down.
SR claims that the speed of light is constant, independent of the motion of the observer, and that, in Einstein’s words, “the same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good” (1905). In simpler terms, the motion of light is relative: you cannot increase your velocity and “catch up” to a beam of light; it will always fly at roughly 300 million metres per second (mps): if you move at 299 million mps, it will fly 300 million mps faster than you. Now, consider two inert percipients, one placed 1000 metres in front of the other. Light, and thus the visual experience of the world, will reach the distant person after it hits the nearer person, despite the fact that they, according to common sense, occupy the same moment in time. But if light hits a person’s eyes before it hits another’s, if one experiences the “present” first, can they both be said to live in the same moment in time?
Obviously, if one is in the present first, then the other, relative to you, is in the past; or, conversely, with you in the present, the other person is in the future. SR mandates that there be past, present and future. If the past and the future are dependent on the frame of reference of an observer, and can be modified by an observer’s position in space, then two events, occurring simultaneously, but in different spacial locations, cannot be said, in any absolute (i.e., non-relative) sense, to occur at the same time. This non-simultaneity is called the “relativity of simultaneity”. In a sense, this multiplicity of time-zones does not invalidate presentism: one can claim that very many present moments exist independently. However, if we acknowledge the existence of other persons, then, under SR, the “absolutism of simultaneity” required of presentists is discredited. However, to discredit presentism does not require us to accept the metaphysical and ontological character of eternalism. Further, intermediary moves are required.
Between 1966 and 1989, a philosophical consequence of SR was formulated, as an analogue, or indispensible counterpart, to eternalism. Called the Rietdijk-Putnam argument, or, alternately, the Andromeda paradox, it argues, in the words of Hilary Putnam, that ‘future things (or events) are already real!” (1967, 242 [emphasis added]). It uses SR and the relativity of simultaneity to postulate a “block universe” existing tenselessly in four dimensions (4D). For the presentist, the world is three-dimensional (3D), with all objects and events existing simultaneously in the “now”. The eternalist takes a 3D object to be just one slice of a 4D universe (block universe) in which all 3D slices (that is, every object, and every conceivable “now”) are present at once. It is difficult to understand a fourth dimension, so let us put it this way. In SR there is no objective frame of reference. According to a percipient’s spatial position and velocity, their plane of simultaneity will be different from everyone else’s. Thus there are as many different present moments as there are percipients. If each percipient lives in a 3D universe, then, in order to unify their relative existence in a unitary universe, we must posit a fourth dimension. Thus each percipient (3D object) is just one slice in a 4D universe, where all percipients (and their place in time relative to one another) exist at once. Under SR, time is eternal and all times co-exist.
A second scientific principle also has great implications for metaphysicians of time. The second law of thermodynamics (2nd law), though commonly used to characterise time as having objective properties and a past, present and future (in that order), is, to the author, a better defender of timeless theory. We will now see why. The 2nd law concerns entropy. Entropy can be roughly defined as the amount of disorder in a physical system. High entropy means high disorder: a high entropy system is disordered because much in the system could be changed and rearranged without anyone noticing. Low entropy means low disorder: if something is highly ordered, moving even a small few things around would be very noticeable. High entropy systems are more disordered because they have more things in them, and thus more things to mix up in a disorderly fashion. As systems become more complex, their entropy increases. This can be formalised as the law that physical systems trend towards states of higher entropy. For example, the gas in a bottle of cola is in a low entropy state: the gas molecules can only rearrange themselves in ways that conform to the shape of the bottle. The same second the cap is removed from the bottle, the gas is able to disperse amongst a greater capacity and diversify in many more physical configurations (Greene 2004, 143-177).
Ludwig Boltzmann concluded from this that there is a general mechanical law that ordered systems become more and more disordered the older they become. This means that, judging from the complexity of this universe, we can (roughly) determine its age; and it having an age means that time, in some sense, exists; and time exists moving forward from past to future, a time direction determined by the law that moves from low to high entropy, that is, that entropy has a one-directional increase with time (call this the arrow of time). Thus the arrow of time provides an excellent scientific rationale for the unilinear progression of time from past to future that informs our everyday experience of the world, and provides, if not a defense of presentism, then a rejection of eternalism. However, this conclusion ultimately turned out to be false. The arrow is an illusion. To quote Karl Popper: ‘[Henry] Poincare had previously proved (and Boltzmann never challenged this proof), that every closed [ordered] system returns, after some finite time, to the neighbourhood of any state in which it was before. Thus all states are (approximately) recurring forever” (2001, 183). And as everything happens all the time, and there is no absolutely preferred direction in which entropy flows, there is no one-directional arrow of time. Rather, the lack of an ontological privileging of any particular time-frame, and the eternality of the universe, conforms most easily with an eternalist metaphysic.
This paper has endeavoured to show that the past and future do exist by making the following expository progression: time is in the mind so does not exist; time, though in the mind, exists, though only as the present; the flow of the time in the present is impossible because events cannot change, so we must substitute tensed reality with tenseless reality, where everything co-exists, nothing changes, and statements about time are observer-dependent (related to observed simultaneity, for example); special relativity confirms that statements about tense cannot be confirmed absolutely, and confirms that different times co-exist; and the arrow of time gives the qualic illusion of flow, but, being illusory, is evidence for the “block universe” in which time is tenseless and exists all at once.
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