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20
PHILOSOPHY OF TIME AND SPACE
And thus much concerning God, to discourse of whom from the appearances of things does certainly belong to Natural Philosophy.
ISAAC NEWTON, MATHEMATICAL PRINCIPLES OF NATURAL PHILOSOPHY
1—INTRODUCTION The philosophy of time and space has traditionally been a branch of metaphysics, but since the early twentieth century it has been subsumed as one of the subdisciplines of philosophy of science. Today mainstream philosophy of time and space is predominantly reflection on time and space as they are described in physics, particularly relativity theory (both special and general) and quantum theory.
Why this dramatic change occurred is itself a matter of considerable philosophical interest. Albert Einstein, in explaining the importance of Ernst Mach’s radical empiricism for the development of the special theory of relativity (STR), once remarked that not even Mach’s opponents realized how much of his philosophy they had imbibed, as it were, with their mother’s milk.1 Much the same could be said of contemporary philosophers of time and space with respect to the philosophy of positivism—a school of thought that was scientistic and deeply antimetaphysical—and its partner, verificationism, according to which an informative sentence, in order to be meaningful, must be capable in principle of being empirically verified. Though these radically empirical perspectives are today almost universally rejected, their legacy lives on in the physical theories predicated on them.
The edifice of twentieth-century physics rests on the twin pillars of relativity theory and quantum theory, and both of these mighty pillars stand
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on the decayed bases of a verificationist epistemology. Not that the mathematical cores of these theories are incorrect (though they are inconsistent with one another and will require some higher-level theory to reconcile them); rather, it is the received physical interpretations of the mathematical equations that are verificationist in essence. This fact ought to arouse a good deal of sympathy for antirealist or instrumentalist construals of these theories. But neither philosophers nor physicists have by and large given up realist construals of these theories for that reason (though realist claims with respect to quantum theory do elicit a good deal of skepticism).
Moreover, philosophical discussion of time and space proceeds almost as if the epistemological revolution that brought about positivism’s demise in the second half of the twentieth century had not occurred. In a survey article titled “Philosophy of Space and Time” in Introduction to the Philosophy of Science, John Norton observes that this discipline exhibits some of the “clearest applications” of the ideas of logical positivism, such as (1) an application of the verification principle of meaning in Einstein’s special theory of relativity in order to eliminate the state of absolute rest posited in Newton’s classical theory of time and space, (2) conventionality claims concerning the metric of space and of time, as well as relations of simultaneity within a single reference frame, and (3) reductionistic analyses of spatiotemporal relations to causal relations in the causal theory of time.2
It is remarkable that while (2) and (3) have largely succumbed to criticism, (1) remains an almost unchallenged dogma. It is frequently said that the advent of relativity theory destroyed the classical conceptions of time and space, forcing us to abandon absolute rest, absolute simultaneity, and even the separability of time and space.
2—RELATIVITY AND THE CLASSICAL CONCEPT OF TIME In order to assess these claims, we must recur to the fount of the classical concept of time, Isaac Newton’s epochal Mathematical Principles of Natural Philosophy (Philosophiae naturalis principia mathematica, 1687). In the scholium (annotation) to his set of definitions leading off the
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Principia, Newton explains his concepts of time and space. In order to clarify these concepts, Newton draws a distinction between absolute time and space and relative time and space:
I. Absolute . . . time, of itself, and from its own nature, flows equably without relation to anything external, and by another name is called duration: relative . . . time, is some sensible and external (whether accurate or unequable) measure of duration by the means of motion, which is commonly used instead of true time; such as an hour, a day, a month, a year.
II. Absolute space, in its own nature, without relation to anything external, remains always similar and immovable. Relative space is some movable dimension or measure of the absolute spaces; which our senses determine by its position to bodies; and which is commonly taken for immovable space; such is the dimension of a subterraneous, an aerial, or celestial space, determined by its position in respect of the earth.3
First and foremost, Newton is here distinguishing between time and space themselves and our measures of time and space. Relative time is the time determined or recorded by clocks and calendars of various sorts; relative space is the length or area or volume determined by instruments like rulers or measuring cups. As Newton says, these relative quantities may be more or less accurate measures of time and space themselves. Time and space themselves are absolute in the sense that they just are the quantities themselves, which we are trying to measure with our physical instruments.
There is a second sense in which Newton held time and space to be absolute, however. They are absolute in the sense that they are unique. There is one, universal time in which all events come to pass with determinate duration and in a determinate sequence and one, universal space in which all physical objects exist with determinate shapes and in a determinate arrangement. Thus Newton says that absolute time “of itself, and from its own nature, flows equably without relation to anything external,” and absolute space “in its own nature, without relation to
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anything external, remains always similar and immovable.” Relative times and spaces are many and variable, but not time and space themselves.
On the basis of his definitions of time and space, Newton went on to define absolute versus relative place and motion:
III. Place is a part of space which a body takes up, and is according to the space, either absolute or relative. . . .
IV. Absolute motion is the translation of a body from one absolute place into another; and relative motion, the translation from one relative place into another.4
By “translation” Newton means transporting or displacement. Absolute place is the volume of absolute space occupied by an object, and absolute motion is the displacement of a body from one absolute place to another. An object can be at relative rest and yet in absolute motion. Newton gives the example of a piece of a ship, say, the mast. If the mast is firmly fixed, then it is at rest relative to the ship; but the mast is in absolute motion if the ship is moving in absolute space as it sails along. Thus two objects can be at rest relative to each other, but both moving in tandem through absolute space (and thus moving absolutely).
In Newtonian physics there is already a sort of relativity. A body that is in uniform motion (that is, no accelerations or decelerations occur) serves to define an inertial frame, which is just a relative space in which a body at rest remains at rest and a body in motion remains in motion with the same speed and direction. Newton’s ideal ship sailing uniformly along would thus define an inertial frame. Although Newton postulated the existence of an absolute inertial frame, namely, the reference frame of absolute space, nevertheless it is impossible for observers in inertial frames that are moving in absolute space to determine experimentally that they are in fact moving. If someone’s relative space were moving uniformly through absolute space, that person could not tell whether he was at absolute rest or in absolute motion. By the same token, if his relative space were at rest in absolute space, he could not know that he was at absolute rest rather than in absolute motion. He could know that his inertial frame was in motion relative to some other observer’s inertial frame (say, another passing ship), but he could not know if either of them were at absolute rest or in absolute motion.
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Thus within Newtonian physics an observer could measure only the relative uniform motion of his inertial system, not its absolute uniform motion.
Newtonian physics prevailed all the way up through the end of the nineteenth century. The two great domains of nineteenth-century classical physics were Newton’s mechanics (the study of the motion of bodies) and Maxwell’s electrodynamics (the study of electromagnetic radiation, including light). The quest of physics at the end of the nineteenth century was to formulate mutually consistent theories of these two domains. The problem was that although Newton’s mechanics was characterized, as we have mentioned, by relativity, Maxwell’s electrodynamics was not. It was widely held that light consisted of waves, and, since waves had to be waves of something (e.g., sound waves are waves of the air, ocean waves are waves of the water), light waves had to be waves of an invisible, all- permeating substance dubbed the aether. As the nineteenth century wore on, the aether was divested of more and more of its properties until it became virtually characterless, serving only as the medium for the propagation of light. Since the speed of light had been measured and since light consisted of waves in the aether, the speed of light was absolute; that is to say, unlike moving bodies, light’s velocity was determinable relative to an absolute frame of reference, the aether frame. To be sure, in the Newtonian scheme of things, moving bodies possessed absolute velocities relative to this frame, but within an inertial frame there was no way to measure what they were. By contrast, since waves move through their medium at a constant speed regardless of how fast the object that caused them is moving, light had a determinable, fixed velocity. So electrodynamics, unlike mechanics, was not characterized by relativity.
But now it seemed that one could use electrodynamics to eliminate relativity. Since light moved at a fixed rate through the aether, one could, by measuring the speed of light from different directions, figure out one’s own velocity relative to the aether. For if one were moving through the aether toward the light source, the speed of light should be measured as being faster than if one were at rest (just as water waves would pass you more rapidly if you were swimming toward the source of the waves than if you were floating motionless in the water); whereas if one were moving through the aether away from the light source, the speed of light would be measured as being slower than if one were at rest (just as the water waves would pass
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you less rapidly if you were swimming away from the source of the waves than if you were floating). Thus it would be possible to determine experimentally within an inertial frame whether one is at rest in the aether or how fast one is moving through it.
Imagine, then, the consternation when experiments, such as the Michelson-Morley experiment in 1887, failed to detect any motion of the earth through the aether! Despite the fact that the earth is orbiting the sun, the measured speed of light was identical no matter what direction their measuring device was pointed. It needs to be underlined how weird the situation was. Waves travel at a constant speed regardless of the motion of their source and in this sense are unlike projectiles, which travel at a velocity that is a combination of the speed of their source plus their speed relative to the source. For example, a bullet fired ahead from a speeding police car travels at a combined speed of the car’s speed plus the bullet’s normal speed, in contrast to sound waves emitted from the car’s siren, which travel through the air at the same velocity whether the car is stationary or in motion. Consequently, an observer who is moving in the same direction as a sound wave will observe it passing him at a slower speed than if he were at rest. If he goes fast enough, he can catch the wave and break the sound barrier. But light waves are different. Light’s measured velocity is the same in all inertial frames, for all observers. This implies, for example, that if an observer in a rocket going 90 percent the speed of light sent a light beam ahead of him, both he and the recipient of the beam would measure the speed of the beam to be the same, and this whether the recipient were standing still or himself moving toward or away from the light source at 90 percent the speed of light.
Desperate for a solution, the Irish physicist George Francis FitzGerald and the great Dutch physicist Hendrik Lorentz proposed the remarkable hypothesis that one’s measuring devices shrink or contract in the direction of motion through the aether, so that light appears to traverse identical distances in identical times, when in fact the distances vary with one’s speed. The faster one moves, the more his devices contract, so that the measured speed of light remains constant. Hence, in all inertial frames the speed of light appears the same. With the help of the British scientist Joseph Larmor, Lorentz also came to hypothesize that one’s clocks slow down when in motion relative to the aether frame. One thus winds up with
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Lorentzian relativity: there exists absolute motion, absolute length, and absolute time, but there is no way to discern these experimentally, since motion through the aether affects one’s measuring instruments. Lorentz developed a series of equations called the Lorentz transformations, which show how to transform one’s own measurements of the spatial and temporal coordinates of an event into the measurements that would be made by someone in another inertial frame. These transformation equations remain today the mathematical core of STR (special theory of relativity), even though Lorentz’s physical interpretation of STR was different from Einstein’s interpretation.
In 1905 Albert Einstein, then an obscure clerk in a patent office in Bern, Switzerland, published his own version of relativity. At this time in his young career, Einstein was still a disciple of the German physicist Ernst Mach. An ardent empiricist, Mach detested anything that smacked of metaphysics and thus sought to reduce statements about time and space to statements about sense perceptions and the connections between them. The young Einstein took what he called his “epistemological credo” from Mach, holding that knowledge is made up of the totality of sense experiences and the totality of concepts and propositions, which are related in the following way: “The concepts and propositions get ‘meaning,’ viz., ‘content,’ only through their connection with sense experience.”5 Any proposition not so connected was literally without content, meaningless. Given such a verificationist criterion of meaning, Lorentz’s absolute time, space, and motion were “metaphysical” notions and therefore meaningless.
Einstein began his 1905 article by jettisoning the aether as superfluous, since, he says, it will not be necessary for the purposes of his paper. Now in order to talk about motion in a physically meaningful way, Einstein claims, we must be clear what we mean by time. Since all judgments about time concern simultaneous events, what we need is a way to determine empirically the simultaneity of distant events. Einstein then proceeds to offer a method of determining, or rather defining, simultaneity for two spatially separated but relatively stationary clocks, that is, two distant clocks sharing the same inertial frame. This procedure will in turn serve as the basis for a definition of the time of an event. He asks us to assume that the time required for light to travel from point A to point B is the same as
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the time required for light to travel from B to A. Theoretically, light could travel more slowly from A to B and more quickly from B to A, even though the round-trip velocity would always be constant. But Einstein says that we must assume that the one-way velocity of light is constant. Having made this assumption, he proposes to synchronize clocks at A and B by means of light signals from one to the other. Suppose A sends a signal to B, which is in turn reflected back from B to A. If A knows what time it was when he sent the signal to B and what time it was when he received the signal back from B, then he knows that the reading of B’s clock when the signal from A arrived was exactly halfway between the time A sent the signal and the time A got the return signal. In this way A and B can arrange to synchronize their clocks. Events are declared to be simultaneous if they occur at the same clock times on synchronized clocks. Using clocks thus synchronized, Einstein defines the time of an event as “the reading simultaneous with the event of a clock at rest and located at the position of the event, this clock being synchronous . . . with a specified clock at rest.”6
By means of these definitions Einstein laid the groundwork for a radically new understanding of time and space. For under the euphemism of disregarding the aether as unnecessary, Einstein abandoned not merely the aether, but, more fundamentally, the reference frame of the aether, or absolute space. Without absolute space there can be no absolute motion or absolute rest. Bodies are moving or at rest only relative to each other, and it would be meaningless to ask whether an isolated body was stationary or uniformly moving per se. Given the constancy of the speed of light in all inertial frames, bodies in motion will be related to each other electrodynamically in such a way that the use of electromagnetic signals to establish synchrony relations between them will play havoc with what we normally mean by simultaneity. What happens is that simultaneity becomes relative. Einstein writes, “Thus we see that we can attribute no absolute meaning to the concept of simultaneity, but that two events which, examined from a co-ordinate system, are simultaneous, can no longer be interpreted as simultaneous events when examined from a system which is in motion relatively to that system.”7 What this means is that events that are simultaneous as calculated from one inertial frame will not be simultaneous as calculated from another. An event that lies in A’s future may be already
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present or past for B! In fact, events that are not causally connected can even be measured to occur in a different temporal order in different inertial frames!
What Einstein did, in effect, was to shave away Newton’s absolute time and space, and along with them the aether, thus leaving behind only their empirical measures. Since these are relativized to inertial frames, one ends up with the relativity of simultaneity and of length. What justification did Einstein have for so radical a move? How did he know that absolute time and space do not exist? The answer, in a word, is verificationism. The introductory sections of the 1905 paper are predicated squarely on verificationist assumptions. These come through most clearly in Einstein’s operationalist redefinition of key concepts.8 The meaning of time is made to depend on the meaning of simultaneity, which is defined locally in terms of occurrence at the same local clock reading. In order to define a common time for spatially separated clocks, we adopt the convention that the time it takes light to travel from A to B equals the time it takes light to travel from B to A—a definition that presupposes that absolute space does not exist. For if A and B are at relative rest but moving in tandem through absolute space, then it is not the case that a light beam will travel from A to B in the same amount of time it takes to travel from B to A, since the distances traversed will not be the same (figure 20.1).
That is why Einstein’s theory, far from disproving the existence of absolute space, actually presupposes its nonexistence. All of this is done by mere stipulation. Reality is reduced to what our measurements read; Newton’s metaphysical time and space, which transcend operational definitions, are implied to be mere figments of our imagination.
It was only by virtue of his verificationism that Einstein could ignore the metaphysical foundations of Newton’s doctrine of absolute time and space. We have already seen that Newtonian time and space are absolute both in the sense that time and space are distinct from our measures of them and in the sense that there is a unique, all-embracing time and a unique, all- embracing space. But Newton also conceived of time and space as absolute in yet a third, more profound sense; namely, he held that time and space exist independent of any physical objects whatsoever. Usually, this is interpreted to mean that time and space would exist even if nothing else
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existed, that we can conceive of a logically possible world that is completely empty except for the container of absolute space and the flow of absolute time.
Figure 20.1. Clock synchronization of relatively stationary clocks in absolute motion. A light signal is first sent A toward B. By the time the signal reaches B, both A and B will have moved together some distance from the point where A first released the signal. Finally, by the time the reflected signal from B reaches A again, both A and B will have moved still farther from the release point. Since the signal traveled farther from A to B than from B back to A, the time it took to travel from A to B is greater than the time it took to travel from B to A.
But here we must be very careful. Modern secular scholars tend frequently to forget how ardent a theist Newton was and how central a role this theism played in his metaphysical outlook. In fact, Newton makes quite clear in the General Scholium to the Principia, which he added in 1713, that absolute time and space are constituted by the divine attributes of eternity and omnipresence. He writes,
He [God] is eternal and infinite; . . . that is, his duration reaches from eternity to eternity; his presence from infinity to infinity. . . . He is not eternity and infinity, but eternal and infinite; he is not
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duration or space, but he endures and is present. He endures forever, and is everywhere present; and, by existing always and everywhere, he constitutes duration and space. Since every particle of space is always, and every indivisible moment of duration is everywhere, certainly the Maker and Lord of all things cannot be never and nowhere.9
Because God is eternal, there exists an everlasting duration, and because he is omnipresent, there exists an infinite space. Absolute time and space are therefore relational in that they are contingent on the existence of God.
In his earlier treatise “On the Gravity and Equilibrium of Fluids,” Newton argued that space (and by implication time) is neither a substance, nor a property, nor nothing at all. It cannot be nothing because it has properties, such as infinity and uniformity in all directions. It cannot be a property because it can exist without bodies. Neither is it a substance: “It is not substance . . . because it is not absolute in itself, but is as it were an emanent effect of God, or a disposition of all being.”10 Contrary to the conventional understanding, Newton here declares explicitly that space is not in itself absolute and therefore not a substance. Rather, it is an emanent —or emanative—effect of God. By this notion Newton meant to say that time and space were the immediate consequence of God’s very being. God’s infinite being has as its consequence infinite time and space, which represent the quantity of his duration and presence. Newton does not conceive of space or time as in any way attributes of God himself, but rather, as he says, concomitant effects of God.
In Newton’s view God’s “now” is thus the present moment of absolute time. Since God is not “a dwarf-god” located at a particular place in space,11 but is omnipresent, there is a worldwide moment that is absolutely present. Newton’s temporal theism thus provides the foundation for absolute simultaneity. The absolute present and absolute simultaneity are features first and foremost of God’s time, absolute time, and derivatively, of measured or relative time.
Thus the classical Newtonian concept of time is firmly rooted in a theistic worldview. What Newton did not realize, nor could he have suspected, is that physical time is not only relative but also relativistic, that
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the approximation of physical time to absolute time depends not merely on the regularity of one’s clock but also on its motion. Unless a clock were at absolute rest, it would not accurately register the passage of absolute time. Moving clocks run slowly. This truth, unknown to Newton, was finally grasped by scientists only with the advent of relativity theory.
Where Newton fell short, then, was not in his analysis of absolute or metaphysical time—he had theological grounds for positing such a time— but in his incomplete understanding of relative or physical time. He assumed too readily that an ideal clock would give an accurate measure of time independent of its motion. If confronted with relativistic evidence, Newton would no doubt have welcomed this correction and seen therein no threat at all to his doctrine of absolute time. In short, relativity corrects Newton’s concept of relative time, not his concept of absolute time.
As a lingering effect of positivism, there is a great deal of antipathy in modern physics and philosophy of science toward such metaphysical realities as Newtonian space and time, primarily because they are not physically detectable. But Newton would have been singularly unimpressed with this verificationist equation between physical undetectability and nonexistence. The grounds for metaphysical space and time were not physical, but philosophical, or more precisely, theological. Epistemological objections fail to worry Newton because, as Oxford philosopher John Lucas nicely puts it, “he is thinking of an omniscient, omnipresent Deity whose characteristic relation with things and with space is expressed in the imperative mood.”12 Modern physical theories say nothing against the existence of such a God or the metaphysical time constituted, in Newton’s thinking, by his eternity. What relativity theory did, in effect, was simply to remove God from the picture and to substitute in his place a finite observer. The theory thus represents, in the words of science historian Gerald Holton, “the final secularization of physics.”13 But to a theist like Newton, such a secular outlook impedes rather than advances our understanding of the nature of reality.
How, then, shall we assess the claim that STR has eliminated absolute time and space? The first thing to be said is that the verificationism that characterized Einstein’s original formulation of STR belongs essentially to the philosophical foundations of the theory. The whole theory rests on
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Einstein’s redefinition of simultaneity in terms of clock synchronization by light signals. But that redefinition assumes necessarily that the time it takes light to travel between two relatively stationary observers A and B is the same from A to B as from B to A in a round-trip journey. That assumption presupposes that A and B are not both in absolute motion, or in other words that neither absolute space nor a privileged inertial frame exists. The only justification for that assumption is that it is empirically impossible to distinguish uniform motion from rest relative to such a frame, and if absolute space and absolute motion or rest are undetectable empirically, therefore they do not exist (and may even be said to be meaningless).
But if verificationism belongs essentially to the foundations of STR, the next thing to be said is that verificationism has proved to be completely untenable and is now outmoded. Verificationism provides no justification for thinking that Newton erred, for example, in holding that God exists in a time that exists independent of our physical measures of it and that may or may not be accurately registered by them. It matters not a whit whether we finite creatures know what time it is in God’s absolute time; God knows, and that is enough.
We are not here endorsing Newton’s views on divine eternity and omnipresence (see chap. 27), but we are contending that such metaphysical considerations as Newton adduced are crucial to a correct understanding of time and space. If we do suppose that God is in time, how then should we understand STR? In a fascinating passage in his essay “The Measure of Time,” Henri Poincaré, the great French mathematician and precursor of relativity, briefly entertains the hypothesis of “an infinite intelligence” and considers the implications of such a hypothesis. Poincaré is reflecting on the problem of how we can apply one and the same measure of time to spatially distant events. What does it mean, for example, to say that two thoughts in two people’s minds occur simultaneously? Or what does it mean to say that a supernova occurred before Columbus saw the New World? Like a good verificationist, Poincaré says, “All these affirmations have by themselves no meaning.”14 Then he remarks,
We should first ask ourselves how one could have had the idea of putting into the same frame so many worlds impenetrable to one another. We should like to represent to ourselves the external
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universe, and only by so doing could we feel that we understood it. We know we can never attain this representation: our weakness is too great. But at least we desire the ability to conceive an infinite intelligence for which this representation could be possible, a sort of great consciousness which should see all, and which should classify all in its time, as we classify, in our time, the little we see.
This hypothesis is indeed crude and incomplete, because this supreme intelligence would be only a demigod; infinite in one sense, it would be limited in another, since it would have only an imperfect recollection of the past; it could have no other, since otherwise all recollections would be equally present to it and for it there would be no time. And yet when we speak of time, for all which happens outside of us, do we not unconsciously adopt this hypothesis; do we not put ourselves in the place of this imperfect God; and do not even the atheists put themselves in the place where God would be if he existed?
What I have just said shows us, perhaps, why we have tried to put all physical phenomena into the same frame. But that cannot pass for a definition of simultaneity, since this hypothetical intelligence, even if it existed, would be for us impenetrable. It is therefore necessary to seek something else.15
Poincaré here suggests that, in considering the notion of simultaneity, we instinctively put ourselves in the place of God and classify events as past, present, or future according to his time. Poincaré does not deny that from God’s perspective there would exist relations of absolute simultaneity. But he rejects the hypothesis as yielding a definition of simultaneity because we could not know such relations; such knowledge would remain the exclusive possession of God himself.
Clearly, Poincaré’s misgivings are relevant to a definition of simultaneity only if one is presupposing some sort of verificationist theory of meaning, as he undoubtedly was. The fact remains that God knows the absolute simultaneity of events even if we grope in total darkness. Nor need we be concerned with Poincaré’s argument that such an infinite intelligence would be a mere demigod, since there is no reason to think that a temporal
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being cannot have a perfect recollection of the past. There is no conceptual difficulty in the idea of a being that knows all past-tense truths. His knowledge would be constantly changing, as more and more events become past. But at each successive moment he could know every past-tense truth that there is at that moment. Hence, it does not follow that if God is temporal, he cannot have perfect recollection of the past.
Poincaré’s hypothesis suggests, therefore, that if God is temporal, his present is constitutive of relations of absolute simultaneity. On this view the philosopher J. M. Findlay was wrong when he said, “The influence which harmonizes and connects all the world-lines is not God, not any featureless, inert, medium, but that living, active interchange called . . . Light, offspring of Heaven firstborn.”16 On the contrary, the use of light signals to establish clock synchrony would be a convention that finite and ignorant creatures have been obliged to adopt, but the living and active God, who knows all, would not be so dependent. In God’s temporal experience, there would be a moment that would be present in absolute time, whether or not it were registered by any clock time. He would know, without any dependence on clock synchronization procedures or any physical operations at all, which events were simultaneously present in absolute time. He would know this simply in virtue of his knowing at every such moment the unique set of present-tense truths at that moment, without any need of physical observation of the universe.
So what would become of STR if God is in time? From what has been said, God’s existence in time would imply that Lorentz, rather than Einstein, had the correct interpretation of relativity theory. That is to say, Einstein’s clock synchronization procedure would be valid only in the preferred (absolute) reference frame, and measuring rods would contract and clocks slow down in the customary special relativistic way when in motion with respect to the preferred frame. Lorentzian relativity is admitted on all sides to be empirically equivalent to Einsteinian relativity, and there are even indications on the cutting edge of science today that a Lorentzian view may be preferable in light of recent discoveries. Such an interpretation would be implied by divine temporality, for God in the “now” of absolute time would know which events in the universe are now being created by him and are therefore absolutely simultaneous with each other and with his
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“now.” This startling conclusion shows that Newton’s theistic hypothesis is not some idle speculation, but has important implications for our understanding of how the world is and for the assessment of rival scientific theories.
3—THE REALITY OF TENSE AND TEMPORAL BECOMING We have seen that for Newton, “time, of itself, and from its own nature, flows equably without relation to anything external.” By the metaphor of time’s flow, Newton expresses his commitment to the objective reality of tense—that is, the moments of time are past, present or future in a mind- independent way—and likewise to the objective reality of temporal becoming, that things come into being and go out of existence as time elapses. Such a view of reality has been called a dynamic or tensed or (in J. M. E. McTaggart’s influential terminology) A-theory of time. By contrast, many philosophers of science hold that tense and temporal becoming are subjective in character. All moments of time are equally existent and are related by the tenseless relations of earlier than, simultaneous with, and later than. The distinction between past, present, and future is not an objective distinction, being merely a subjective feature of consciousness. For the people located in 1868, for example, the events of 1868 are present, and we are future; by the same token, for the people living in 2050 it is the events of 2050 that are present, and we are past. If there were no minds, there would be no past, present, or future. There would be just the four- dimensional space-time universe existing as a block. Such a view of time has been called a static or tenseless or B-theory of time. The question of whether an A- or a B-theory of time is correct has been called “the most fundamental question in the philosophy of time.”17
It is admitted on both sides of the debate that the ordinary, commonsense view is that there is an objective distinction between past, present, and future. We experience the reality of tense in a variety of ways that are so evident and so pervasive that the belief in the objective reality of tense is a universal feature of human experience. Psychologist William
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Friedman, who has made a career of the study of our consciousness of time, reports that “the division between past, present, and future so deeply permeates our experience that it is hard to imagine its absence.”18 He says that we have “an irresistible tendency to believe in a present. Most of us find quite startling the claim of some physicists and philosophers that the present has no special status in the physical world, that there is only a sequence of times, that the past, present, and future are only distinguishable in human consciousness.”19
Consequently, virtually all philosophers of time and space, even those who hold to a B-theory of time, admit that the view of the common man is that time involves a real distinction between past, present, and future. One advocate of the static view grumps that the dynamic understanding of time is so deeply ingrained in us that it seems “programmed by original sin”!20
The advocate of the A-theory of time may plausibly contend that our experience of tense ought to be accepted as veridical, or trustworthy, unless we are given some more powerful reason for denying it.
The A-theorist might formulate an argument to the effect that the objective reality of tense is the best explanation of our experience of tense. But our belief in the reality of tense is much more fundamental than such an argument suggests. We do not adopt the belief in an objective difference between the past, present, and future in an attempt to explain our experience of the temporal world. Rather, our belief in this case is what epistemologists call “a properly basic belief” (recall discussion in chap. 7).
A belief’s being properly basic implies that one is justified in holding to that belief unless and until it is defeated. We may say that such a belief is justified at face value (prima facie). For example, take the belief “The external world is real.” It is possible that you are really a brain in a vat of chemicals, being stimulated with electrodes by some mad scientist to believe that you are reading this book. Indeed, there is no way to prove this hypothesis wrong. But that does not imply that your belief in the reality of the external world is unjustified. On the contrary, it is a properly basic belief grounded in your experience and as such is justified until some defeater comes along. This belief is not defeated by the mere possibility that you are a brain in a vat. For there is no warrant for thinking that one is, in fact, a brain in a vat. Indeed, our belief in the reality of the external world is
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so deeply ingrained and strongly held that any successful defeater of this belief would have to possess enormous warrant. In the absence of any successful defeater, we are perfectly justified in taking our experience of the external world to be veridical.
Now the advocate of an A-theory of time may argue similarly concerning our belief in the past, present, and future. Belief in the objective reality of tense is a properly basic belief that is universal among humankind. It therefore follows that anyone who denies this belief (and who is aware that he has no good defeaters of that belief) is irrational. For such a person fails to hold to a belief that is for him properly basic.
Sometimes advocates of a B-theory of time assert that our experience of past, present, and future need not be taken as veridical, since we can imagine a universe exactly like this one that is a four-dimensional block universe containing individuals whose mental states correspond exactly to our mental states in this world. “But then surely our copies in the block universe would have the same experiences that we do—in which case they are not distinctive of a dynamic universe after all. Things would seem this way, even if we ourselves were elements of a block universe.”21 But this is like arguing that because a brain in a vat would have the same experiences of the external world that we do, therefore we no longer have any grounds for regarding our experiences as veridical! In the absence of some sort of defeater of beliefs grounded by such experiences, these experiences do provide warrant for those beliefs.
Is, then, belief in the objective reality of tense properly basic? To begin with the most obvious, we experience events as present. Our belief that events are happening presently is really no different from our belief that they are happening—and this latter belief is a basic belief grounded in our perceptual experience.
D. H. Mellor, as a proponent of the static view of time, does not believe that there really is a present. Therefore, we cannot, despite appearances, be experiencing it. Mellor thus goes to great lengths to explain away our experience of the present. First, he argues that we do not really observe the tense of events. He gives an illustration of observing astronomical events through a telescope. When we look at the stars, we seem to be observing the events as presently happening; but we know that they actually occurred
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millions of years ago. Thus what we see is the order in which events occurred, but our observations do not tell us the tense of the events. Therefore, when we think that we are observing any event to be present, we are simply confused. We do not observe the event itself to be present; rather, we observe our experience of the event to be present.
However, it seems that Mellor’s objection is ineffective against the argument as we have framed it. For clearly one does not form a belief like “The phone is ringing” by inferring it from a more foundational belief like “My experience of the phone’s ringing is present.” Typically, one does not form any belief like the latter at all. One’s beliefs about the tense of events is not inferred, but basic. As for the illustration of events viewed through a telescope, all that proves is that our beliefs about the tense of events is defeasible and sometimes wrong. One might as well argue that perceptual beliefs are not properly basic because things viewed through a microscope are observed to be larger than they are! Just because our sense perceptions are sometimes mistaken is no reason to think that we do not perceive things. In the same way, mistaken observations of the presentness of certain events do not prove that we make no such observations. In most cases, the events we observe fall within the limits of the psychological present, so that our observations of events as present are veridical and our judgments to that effect properly basic.
In any case, Mellor admits that we do observe our experiences to be present. This is the so-called presentness of experience. Even if we can be mistaken about the presentness of a supernova observed through a telescope, we cannot be mistaken about the presentness of our experience of observing the supernova. If we observe our experiences to be present, aren’t we observing the tense of these mental events?
No, replies Mellor, for “although we observe our experience to be present, it really isn’t.”22 This is a paradoxical statement. Mellor admits that when we make the judgment that our experience is present, we cannot be mistaken. He writes,
So judging my experience to be present is much like my judging it to be painless. On the one hand, the judgment is not one I have to make. . . . But on the other hand, if I do make it, I am bound to be right, just as when I judge my experience to be painless. The
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presence of experience . . . is something of which one’s awareness is infallible.
. . . No matter who I am or whenever I judge my experience to be present, that judgment will be true.23
But if our observation of the presentness of our experience is analogous to our observation of whether our experiences are painful, if we are bound to be right in judging our experience to be present, if our awareness of the presentness of our experience is infallible, if our judgment that our experience is present will be true every time, then how can it be the case that, as Mellor says, “it really isn’t”? If one’s belief that “my experience of observing the supernova is present” is indefeasible, as Mellor admits, then how can that experience not be present, even if the supernova itself is not?
Mellor’s answer is that while the belief that one’s experience is present may have important cognitive significance, nonetheless the factual content of that belief is a tautology and therefore trivial. Mellor maintains that the following belief (A) is just true by definition:
A. The experiences that I am now having possess the property of being present.
He makes this claim because (A) is true if and only if (B):
B. The experiences that I have at the time of the utterance of (A) possess the property of existing at the time of the utterance of (A).
But (B) is trivially true, a mere tautology. Therefore, although (A) is true, its factual content, as disclosed by (B), does not imply the objective reality of presentness.
This response by Mellor is multiply flawed. First, Mellor’s tautology is self-constructed, for he stipulates that it is “the experiences that I am now having” that are judged to be present. But there is no reason to describe one’s experiences as those one is now having. The beliefs in question are not like (A); rather, they are like (A’):
A’. My experience of seeing the supernova is present.
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And (A’) is not tautologous. Second, even (A) can be read in a way that is not tautologous. Let the
phrase “the experience that I am now having” pick out a specific, unique experience like observing the supernova. In that case, the ascription of presentness to that particular experience out of all the experiences one ever has is not trivial or true by definition.
Third, even if (A) is trivial, that does not imply that the presentness of the experience is trivial. It may be trivial to assert that “my present experiences are present” or that “my present experiences are experiences.” But that does nothing to explain away the fact that one does have present experiences or to defeat the belief in the presentness of one’s experiences.
Fourth, stating tenseless truth conditions for one’s belief in the presentness of his experience does not constitute even a prima facie defeater of that belief. Such truth conditions are just irrelevant to the proper basicality of that belief. For the object of one’s belief is not the fact that is stated as the tenseless truth conditions of what one believes. In order for that to be the case, (B), the statement of the truth conditions, would have to have the same meaning as (A), the statement of the tensed belief—which Mellor himself denies. Since they are not synonymous, the triviality of the statement of the truth conditions does not imply the triviality of the tensed belief. Nor is there any reason to think that the factual content of the tensed belief is given exhaustively in the tenseless truth conditions.
It therefore seems that Mellor has not provided a successful defeater of our belief that our experiences are present. Not only does such a belief seem to be properly basic, but it even seems to be indefeasibly true.
A second way in which we experience the reality of tense is exhibited by our attitudes toward the past and future. We recall past events with nostalgia or regret, whereas we look forward to future events with either dread or anticipation. The beliefs that these attitudes express are tensed beliefs. As the late Oxford tense logician A. N. Prior once remarked, when we say, “Thank goodness that’s over!” we certainly do not mean “Thank goodness the date of that thing’s conclusion is June 15, 1954!” or “Thank goodness that thing’s conclusion is simultaneous with this utterance!”—for why should anyone thank goodness for that?24 Prior’s point is that such attitudes cannot concern tenseless facts but are about tensed facts. The
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further point is that it is entirely rational to have such attitudes. Therefore, the tensed beliefs evinced by these attitudes must be rational as well. If it is rational for a person to be relieved that his visit to the dentist is past, then his belief that his visit is past is also rational.
On the B-theory of time, feelings of relief and anticipation must be ultimately regarded as irrational, since events really are not past or future. Yet one can safely say that no B-theorist has ever succeeded in divesting himself of such feelings. Indeed, anyone who did succeed in ridding himself of such feelings and the tensed beliefs they express would cease to be human.
In response B-theorists concede that such attitudes do express tensed beliefs; but they again try to strip those beliefs of any tensed factual content. They say that we thank goodness that our headache is over not because it is over but because we believe it to be over; and the content of this belief is fixed by its tenseless truth conditions, such as the headache’s being earlier than the time of one’s belief. Thus one’s truly believing that his headache is over does not imply that one’s headache is objectively past.
Now certainly B-theorists are correct that what our attitudes immediately express are tensed beliefs, not tensed facts. For an anticipated event may be avoided and so never come to pass at all. But all that proves is that one’s tensed beliefs are defeasible. Many times, however, our tensed beliefs are correct. Indeed, sometimes they are indefeasibly correct, as when one believes that the pain he felt is over. In other words, the question comes down once more to the presentness of experience. When one feels relief, what one is relieved about can be analyzed as a complex fact involving the beliefs that (1) one’s experience is present and (2) some event is earlier than the present. One can be mistaken about (2), but one cannot be mistaken about (1), and thus the objectivity of tense remains.
There is a further feature of our attitudes toward the past and future which deserves to be highlighted, namely, the difference in how we regard an event depending on its pastness or futurity. An unpleasant experience that lies in the future occasions feelings of dread; but that very same experience, once past, evokes feelings of relief. On an A-theory of time these different attitudes are grounded in the reality of temporal becoming. A future event has yet to exist and will be present; but a past event no longer exists and was present. Therefore, it is rational to have different feelings
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about these events. But on a B-theory of time, this difference in attitude toward the past and future is groundless and, hence, irrational. As philosopher of time George Schlesinger points out, on the B-theory of time there is no more difference between an event’s being located one hour later versus one hour earlier than now than there is in an event’s being located one mile to the right versus one mile to the left of here, for neither “now” nor “here” is objective. Whether past or future, both events are equally real, there is no temporal becoming, nor are we moving toward one event and away from the other, and the distinction between past and future is purely subjective. Therefore, it just makes no sense to look on these events differently. And yet, as Schlesinger observes, such a differential concern is a universal human experience.
Think, for example, of the difference in our attitude toward one’s birth and one’s death. On the B-theory of time the period of personal nonexistence that lies after one’s death is of no more significance than the period of personal nonexistence that lies before one’s birth. And yet we celebrate birthdays, whereas we typically dread dying, a dread that runs so deep that one’s death, wholly in contrast to one’s birth, seems to put a question mark behind the value of life itself. Many existentialist philosophers have said that life becomes absurd in light of “my death”; but no one has said this as a result of “my birth.”
B-theorists have naturally been reluctant to dismiss as irrational our differential attitudes toward past and future events and so have instead tried to find some basis for this difference in the static theory. For example, Nathan Oaklander, an ardent defender of static time, insists that such a difference is rational because on the B-theory time is asymmetric; that is to say, there is a direction of time as determined by the ordering of events according to the relations earlier than/later than. Oaklander thinks that it makes all the difference in the world whether an event is later than one’s location in time or earlier than one’s location.
But it is evident that on a B-theory of time the mere asymmetry of time —its having direction according to the relations earlier than/later than—is not an adequate substitute for temporal becoming. Stripped of all tense, the relations of earlier than/later than with respect to some event no more justify differing attitudes on our part than would the relations to the right of/to the left of. Indeed, on the B-theory of time, there are really two
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directions to time: one the “earlier than” direction and the other the “later than” direction. In the absence of temporal becoming it is wholly arbitrary how these directions are laid on the series of events. The two arrows of time could be turned 180 degrees without any inconsistency with the facts. Although some scientists try to appeal to the laws of thermodynamics or other physical processes to establish the single arrow of time, all such attempts presuppose a prior choice of direction—for example, that the direction of entropy increase is the later than direction. In the absence of temporal becoming, such a choice is wholly arbitrary. We could have called the direction of entropy increase earlier than if we had wanted to. Thus earlier and later simply do not have the significance on a B-theory of time that they do on a dynamic theory.
Our differing attitudes toward past and future events serve to underline how deeply ingrained and how strongly held our tensed beliefs are. If the B- theory of time is correct, feelings of relief, nostalgia, dread, and anticipation are all irrational. Since such feelings are ineradicable, the B-theory would condemn us all to irrationality. In the absence of any defeater for our belief in the objective distinction between past, present, and future, such a belief remains properly basic and the feelings they evoke entirely appropriate.
There are many other ways in which we experience the objective reality of tense and temporal becoming. Unless B-theorists are able to come up with some more powerful warrant for adopting a B-theory of time, we ought to stick with the A-theory. So what reasons are there for thinking that a B-theory of time is true?
Undoubtedly, the major motivation for the adoption of a B-theory of time by philosophers of science is the conviction that relativity theory demands it. As Einstein himself came to realize, his special theory makes the most sense if it is formulated in a geometry of four dimensions, and his general theory of relativity characterizes gravity, not as a force, but as the curvature of four-dimensional space-time (the union of space and time into a single reality, which is presupposed by a geometrical approach to gravitation). But from what has already been said above, it is clear that such an argument is not at all compelling. First, there is an interpretation of the mathematical core of special relativity that is empirically equivalent to the Einsteinian interpretation and is fully compatible with an A-theory of
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time, namely, Lorentzian relativity. So what is wrong with a Lorentzian interpretation?
Verificationism aside, at the root of many physicists’ aversion to Lorentzian relativity is the conviction that comes to expression in Einstein’s aphorism: “Subtle is the Lord, but malicious He is not.” That is to say, if there exists in nature a fundamental asymmetry, then nature will not conspire to conceal it from us. But Lorentzian relativity requires us to believe that although absolute simultaneity and length exist in the world, nature conceals these from us by slowing down our clocks (clock retardation) and shrinking our measuring rods (length contraction) when we try to detect them. D’Abro voices his objection to such a conspiracy of nature:
If Nature was blind, by what marvelous coincidence had all things been so adjusted as to conceal a velocity through the ether? And if Nature was wise, she had surely other things to attend to, more worthy of her consideration, and would scarcely be interested in hampering our feeble attempts to philosophize. In Lorentz’s theory, Nature, when we read into her system all these extra-ordinary adjustments ad hoc, is made to appear mischievous; it was exceedingly difficult to reconcile one’s self to finding such human traits in the universal plan.25
It must first be said that d’Abro greatly exaggerates the extent of the alleged conspiracy. After all, special relativity is a restricted theory: it is only uniform motion relative to the privileged reference frame that is concealed from us. But acceleration and rotation are absolute motions that nature does nothing to conceal. Furthermore, one must surely question the presupposition that if fundamental asymmetries exist, nature must disclose these to us. The empirical manifestation of an underlying state of nature may often appear altered as a result of distortions that intervene between theory and evidence, so that it is a nontrivial task to excavate the state of nature from its distorted manifestation. Tim Maudlin, a philosopher of science who has specialized in the implications of so-called quantum nonlocality for relativity theory, concludes after surveying all the attempts to integrate the results of Bell’s theorem with relativity theory, “One way or
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another God has played us a nasty trick.”26 He maintains that the solution of Lorentzian relativity cannot be rejected on the grounds that it would be deceptive of nature, for the partisans of all the solutions say the same thing about all the others. In the end, he muses, “The real challenge falls to the theologians of physics, who must justify the ways of a Deity who is, if not evil, at least extremely mischievous.”27
As for d’Abro’s complaint about finding “human traits in the universal plan,” the Lorentzian might in response appeal to the so-called anthropic principle. According to that principle, features of the universe can be seen in the correct perspective only if we keep in mind that certain features of the universe are necessary if observers like us are to exist. If the universe were not to have those features, then we would not be here to observe the ones it has. Now our very existence depends on the maintenance of certain states of equilibrium within us. But length contraction and clock retardation are, on the Lorentzian view, the result precisely of material systems’ maintaining their equilibrium states while being in motion. Thus, if nature lacked this compensating behavior, we would not be here to observe the fact! Given that we could not exist without it, why should we be surprised at observing nature’s “conspiracy”?
But why is nature structured in such a way? Given the theistic perspective from which we approach these questions, we should hardly be surprised at discovering that the universe is designed in such a way as to support our existence. We should expect that God will have chosen laws of nature that will maintain the equilibrium states essential to our existence. Even if, as d’Abro puts it, Nature is blind, God is not; and if Nature is not wise, God is. It is not Nature, then, who is concerned with our feeble selves, who deems us worthy subjects to attend to, but the Creator and Sustainer of the universe who is mindful of man (Ps 8:3-8). Subtle is the Lord, merciful he is also.
As for the general theory of relativity, the question raised by Einstein’s geometrical approach to gravitation is whether it is to be understood realistically or merely instrumentally. According to the noted philosopher of science Arthur Fine, few working, knowledgeable scientists give credence to the realist construal of general relativity. Rather, the theory is seen as “a magnificent organizing tool” for dealing with gravitational problems: “Most
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who actually use it think of the theory as a powerful instrument, rather than as expressing a ‘big truth.’”28 It can be safely said that no scientific disadvantage arises from treating the geometrical approach to gravity as merely instrumental. Indeed, on the contrary, it can be argued that a realist understanding of space-time actually obscures our understanding of nature by substituting geometry for a physical gravitational force, thus impeding progress in connecting the theory of gravity to the theory of particles. In his Gravitation and Cosmology, the Nobel Prize–winning physicist Steven Weinberg contends that taking gravity to be a real force is “a crucial link” between general relativity and particle physics, since there must then be a particle of gravitational radiation, the so-called graviton.29 The geometrical approach of space-time realism is thus a positive impediment to our gaining a more integrated understanding of physics. Geometrical space-time, in Weinberg’s view, should be understood “only as a mathematical tool” and “not as a fundamental basis for the theory of gravitation.”30
What other reasons might be offered for adopting a B-theory of time? One of the most celebrated arguments is McTaggart’s paradox. In 1908 the Cambridge idealist John Ellis McTaggart published a remarkable article in the journal Mind titled “The Unreality of Time.”31 His argument consists of two parts. In the first part McTaggart argues that time is essentially tensed. In the second part he argues that tensed time is self-contradictory. It therefore follows that time is unreal.
Since our concern is with arguments for the B-theory of time, we shall focus on the second half of McTaggart’s proof. His argument here is apt to appear bewildering unless we first understand its metaphysical presuppositions. The key to understanding the contradiction McTaggart sees in a tensed view of time is his presupposition that past, present, and future events are all equally real or existent and that temporal becoming consists in the movement of the present along this series. McTaggart thinks of the series of temporal events as stretched out like a string of light bulbs that are each momentarily illuminated in succession, so that the light is seen to move across the series of bulbs. In the same way presentness moves across the series of events. Since all events are equally existent, the only respect in which they change is the change in tense that they undergo. First they are future, then they are present, then they are past. In every other respect they
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just are. Obviously, then, for McTaggart becoming present does not imply becoming existent.
McTaggart observes that pastness, presentness, and futurity are mutually incompatible: no event can have all three. But given McTaggart’s tenselessly existing series of temporal events, every event does have all three! Take an event tenselessly located at t1. At t1 that event is obviously present. But because all events are equally real, that same event also has pastness and futurity because at t2 it is past and at t0 it is future. The moment t1 is not any more real or privileged than t0 or t2, and so the event in question must be characterized by the tenses it has at all these times, which is impossible. We can visualize the problem by imagining the people existing at each of these three moments. For the people at t1, t1 is present. Since neither t1 nor these people pass away, it is still the case when it is t2 that for the people at t1 the moment t1 is present. But for the people at t2 the moment t1 is past. The moment t1 never sheds presentness and takes on pastness—just ask the people at t1! But t1 never exchanges its pastness for any other tense either, as the people at t2 will tell you. Thus t1 is changelessly both present and past, which is impossible. If someone should say, “But t1 is present relative to t1 and past relative to t2, which is not contradictory,” the advocate of tenseless time will say that such relational properties reduce to the tenseless relations is simultaneous with and is earlier than, which vindicates the tenseless theory.
After decades of discussion, a consensus seems to be emerging that McTaggart’s paradox is based on a misguided attempt to marry a dynamic theory of temporal becoming to a static series of events. It is then no wonder that the dynamic-static theory of time he winds up with proves to be self-contradictory! Sharp-sighted critics of McTaggart such as C. D. Broad and A. N. Prior have insisted almost from the beginning that a tensed or A- theory of time implies a commitment to presentism, the doctrine that the only temporal entities that exist are present entities. According to presentism, past and future entities do not exist. Thus there really are no past or future events, except in the sense that there have been certain events and there will be certain others; the only real events are present events. Thus there can be no question of an event’s swapping futurity for
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presentness or cashing in presentness for pastness. Temporal becoming is not the exchange of tense on the part of tenselessly existing events, but the coming into and going out of existence of the entities themselves. Events no more change tenses than they exchange properties of nonexistence and existence! An event possesses only the tense it has when it is present, namely, presentness. No event ever possesses pastness or futurity, for nonpresent events do not exist. Thus there can be no question of any event’s possessing incompatible tense determinations. Thus McTaggart’s paradox is ineffectual against the presentist. The paradox arises, not from a contradiction within a tensed theory of time, but from a misconceived union of the A- and B-theories of time.
Presentism is not infrequently rejected because it is thought to imply, in conjunction with STR, a sort of solipsism (the view that I alone exist), which no sane person can believe. This unwelcome consequence is due to the absence of absolute time and space within the context of STR, which makes it impossible to define any plausible coexistence relation between oneself and other things. Anyone who has followed our argument thus far, however, will realize that this objection to presentism is not difficult to answer. It is predicated on an Einsteinian interpretation of relativity theory, which one may reject on wholly independent grounds in favor of a Lorentzian interpretation. A Lorentzian understanding of relativity preserves relations of absolute simultaneity and so confronts no challenge concerning coexistence relations among temporal beings. The presentist who accepts Lorentzian relativity is thus not threatened by the specter of solipsism.
In conclusion, we have good grounds for accepting an A-theory of time in view of the proper basicality of our belief in the objective reality of tense and temporal becoming. By contrast, arguments for a B-theory of time tend to rely on a physical interpretation of relativity theory that is founded on an untenable verificationist epistemology. In general, contemporary philosophy of time and space has, as a result of the positivist era, been thoroughly infected by an unhealthy scientism. It is high time for philosophy of time and space to be restored to the domain of philosophy where it properly belongs: metaphysics, where theistic considerations, such as Newton adduced, cannot be ignored.
Moreland, J. P., & Craig, W. L. (2017). Philosophical foundations for a christian worldview. InterVarsity Press. Created from liberty on 2025-02-11 16:36:55.
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CHAPTER SUMMARY Traditionally a topic handled in metaphysics, philosophy of time and space as practiced today has been absorbed into philosophy of science. This is the lingering effect of the acid bath of verificationism and positivism, which dominated philosophy during the first half of the twentieth century. In particular, verificationist analyses of key concepts like time and simultaneity lie essentially at the epistemological foundations of relativity theory, the principal domain of physics addressing problems of time and space. The demise of positivism reopens the traditional metaphysical problems of time and space. In dealing with such questions one cannot ignore the philosophical impact of the existence of God, which lies at the metaphysical foundations of the classical concept of time and space.
One of the most important metaphysical questions about the nature of time concerns the status of tense and temporal becoming. Partisans of a tensed or A-theory of time can plausibly argue that in light of our temporal experience our belief in the objective difference between past, present, and future is a properly basic belief. Advocates of a tenseless or B-theory of time appeal in vain to relativity theory to defeat this conclusion, since there are plausible interpretations of that theory that are consistent with an A- theory. Moreover, objections based on McTaggart’s paradox may be turned back by adoption of a metaphysic of presentism.
CHECKLIST OF BASIC TERMS AND CONCEPTS A-theory of time (dynamic or tensed theory of time)
absolute motion
absolute place
absolute space
absolute time
aether
Moreland, J. P., & Craig, W. L. (2017). Philosophical foundations for a christian worldview. InterVarsity Press. Created from liberty on 2025-02-11 16:36:55.
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anthropic principle
arrow of time
asymmetry of time
B-theory of time (static or tenseless theory of time)
clock retardation
clock synchronization
constancy of the speed of light
direction of time
eternity
general theory of relativity
geometrical approach to gravitation
inertial frame
length contraction
Lorentz transformations
Lorentzian relativity
Maxwell’s electrodynamics
McTaggart’s paradox
Michelson-Morley experiment
Newton’s mechanics
omnipresence
one-way velocity of light
operationalist definition
particle physics
positivism
Moreland, J. P., & Craig, W. L. (2017). Philosophical foundations for a christian worldview. InterVarsity Press. Created from liberty on 2025-02-11 16:36:55.
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presentism
presentness of experience
relative space
relative time
relativity of length
relativity of simultaneity
simultaneity
solipsism
space-time
special theory of relativity
speed of light
temporal becoming
tense
time’s flow
uniform motion
verificationism
Moreland, J. P., & Craig, W. L. (2017). Philosophical foundations for a christian worldview. InterVarsity Press. Created from liberty on 2025-02-11 16:36:55.
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