What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know.—Augustine, Confessions
Augustine’s account of time is often praised as unique among the philosophical doctrines found in late antiquity, but in the same laudatory breath, commentators almost always reject his ideas. This dual response finds popular voice in Bertrand Russell’s A History of Western Philosophy, in which he states that although he disagrees with Augustine’s conclusions, it is a “great advance on anything to be found on the subject in Greek philosophy.” According to this traditional interpretation, Augustine argues for a subjective idealism regarding time wherein time is dependent on the human mind and is upheld by the mental attitudes of expectation, attention, and memory. Philosophers claim that a purely subjectivist conception of time, though intriguing, is unable to make sense of our best scientific theories. And theologians like Robert W. Jenson have even described Augustine’s account of time as a deeply confused artifact of his incompatible commitments to Neoplatonism and Christianity.1
In contrast, I argue that Augustine’s view of time is both similar to our current scientific understanding of time and theologically useful. Once we understand Augustine’s approach, both in the context of his time and our own, I believe we can find insight about time as such and learn an important lesson about appropriate methodology for Christian philosophers and theologians.2
Augustine’s Philosophy of Time
Augustine’s discussion of time in book 11 of the Confessions starts, much like Plato, with a discussion of eternity. He begins by considering a question often raised by pagan skeptics, “What was God doing before he created?” and then quickly dismisses this question for overlooking a crucial difference between eternal and temporal processes. As he puts it, echoing Aristotle, time does not lengthen except by the passage of events, whereas eternity is characterized by simultaneity.3 Eternity “expresses” itself in the past and future, but because it “stands still,” it is not itself either past or future but instead “forever present.”And thus, for Augustine, there is no sense in asking what an eternal God was doing before creation. From this initial discussion two things seem clear. First, Augustine, like many of his contemporaries, sees change as essential to temporal processes. Second, like Plato (and the Neoplatonists), he believes that eternity has metaphysical priority and perhaps plays a causal role in generating time.
Augustine then considers the paradoxes of time that influenced the Hellenistic schools. Like Aristotle and the Stoics, Augustine wonders whether the instability of the past and the future, the constant movement of events from one to another, undercuts the existence of time as such. Augustine notes that the present only makes sense as time insofar as it “moves” into the past, because time cannot “abide.” But this conclusion, he acknowledges, is paradoxical, for it seems that the cause of the present’s being is that it will cease to be.4
To address this paradox, Augustine considers measurement. He notes that although we often speak of a period of time being long or short—a kind of measuring—“in what sense is something long or short that is nonexistent?” Augustine resists the skeptical conclusion that our talk about time is meaningless. We have a common and well-established practice of measuring time, so for this practice to be meaningful time must have some reality.5 As he considers this point, Augustine is wrestling with the traditional Aristotelian paradoxes of time from various angles and not yet presenting a positive argument of his own.6 The puzzle of time, he suggests, is that there seems to be no backdrop against which we can measure its length; everything we could use as a measurement is in time.7
Augustine then makes the argument thought to directly support a subjective conception of time:
The extendedness may be of the mind itself. For what is it I measure, I ask thee, O my God, when I say either, roughly, “This time is longer than that,” or, more precisely, “This is twice as long as that.” I know that I am measuring time. But I am not measuring the future, for it is not yet; and I am not measuring the present because it is extended by no length; and I am not measuring the past because it no longer is. What is it, therefore, that I am measuring? Is it time in its passage, but not time past [praetereuntia tempora, non praeterita]?8
Augustine thus presents two options: (1) what we measure is an extendedness of the mind or (2) what we measure is time in its passage, not in its state as future, past, or static present.9
In a subsequent section, Augustine argues that it is impossible for us to measure time in its passage because of the unextendedness of the present.10 This leaves the first option, that time is an extendedness of mind. Indeed, Augustine seems to settle on this definition, pointing to memory, and then attention and expectation, as mental faculties that give rise to time. As he says:
It is in you, O mind of mine, that I measure the periods of time. Do not shout me down that it exists [objectively]; I do not overwhelm yourself with the turbulent flood of your impressions . . . I measure as time present, the impression that things make on you as they pass by and what remains after they have passed by—I do not measure the things themselves which have passed by and left their impression on you. . . . Either, then, these are periods of time, or else I do not measure time at all.11
This is the basis for the subjectivist reading of Augustine’s philosophy of time. Some might try to resist a merely subjective interpretation by proposing that in this “extendedness of mind” we find an epistemic solution about how people measure time, not a metaphysical argument about the nature of time itself. Against Augustine’s direct statements like “Either, then, these [mental impressions] are the periods of time, or else I do not measure time at all,” we could respond that Augustine only affirms the second half of that disjunction—we do not, strictly speaking, measure time. Given that Augustine needs extension for measurement, it cannot be the nonextended present moment of fleeting time that is measured directly. Rather, the impressions created in the mind by temporal change also create a measurable spatial extension—the space of memory. So according to this view, the traditional subjectivist interpretation of time in Augustine concerns, as Jason Carter words it, “time’s effects, but not about the nature of time itself.”12
This passage, however, describes more than an epistemic feature. Augustine thinks that a particular concept of time—“deictic” time—metaphysically (not just epistemically) depends on minds. That term, deictic,comes from linguistics and is used to describe words that mean the same thing but refer to different things depending on their context. For example, here, now, and I are all deictic words. They each have the same meaning no matter who speaks them, but they pick out different things depending on who speaks. Deictic time is the supposedly objective now that we all experience from within our own independent contexts, and Augustine connects this idea to a certain notion of change. For Augustine, deictic time is “flowing time.” Whereas eternity “abides,” temporal deictic time passes through past, present, and future; it passes out of being.13 Augustine claims, then, that there is one objectively existing time, the present, and that the other “times” are just shorthand for operations the mind performs on that fleeting present. As he states,
It is manifest and clear that there are neither times future nor times past . . . perhaps it might be said rightly that there are three times: a present of things past; a present of things present; and a time present of things future. For these three do coexist somehow in the soul, for otherwise I could not see them.14
What, then, is the relationship between the mentally dependent features of deictic time and objective change?15 For Augustine, change gives rise to deictic time in conjunction with some continuity against which the change is ordered or measured, and for humans that continuity is the mind. As Augustine says, “Our attentionhas a continuity, and it is through this that what is present may proceed to become absent.” Evidence for this interpretation is found later in the Confessions in Augustine’s discussion of creation. There, he states that change gives rise to time but that “where there is no shape or order there is nothing that either comes or goes, and where this does not occur there certainly are no days, nor any vicissitude of duration.”16 This reading of Augustine is closer to Aristotle in that it links objective time to some sort of, in principle, numerical measure of change.
Further supporting this connection, there is a passage in The City of God in which Augustine again discusses the relationship between change and time. He claims the following:
For, if eternity and time are rightly distinguished by this, that time does not exist without some movement and transition, while in eternity there is no change, who does not see that there could have been no time had not some creature been made, which by some motion could give birth to change—the various parts of which motion and change, as they cannot be simultaneous, succeed one another—and thus, in the shorter or longer intervals of duration, time would begin?17
As some have noted, Augustine here links time’s dependence on motion to the Aristotelian idea that substances cannot simultaneously hold contrary attributes. Changing from one attribute to another is marked off by time because the coming to be and passing away of properties is measured against the continuity of substance, a reading of change and time that is reinforced by Augustine’s implicit use of Aristotle’s categories in The Trinity.18 Here, Augustine affirms, like Aristotle, that substance is the primary category, with others inhering in or depending on it, and he characterizes time as a secondary category. Thus, time is not a substance for Augustine, but it must exist relative to a substance.19
For Augustine, objective time is the gaining and passing away of propertiesthat are predicated of an enduring substance, where that “gaining and passing away” is described as motion or change—physical, mental, or spiritual—within the created order. I claim, in addition, that for humans the relevant substance is, most fundamentally, our souls or intellects (what moderns call minds). Accordingly, our epistemic access to time is through the accidental predication of our mental substance. The continuity of this substance allows us to recognize the gaining and passing away of the mental impressions upheld by memory, attention, and expectation. Thus, the traditional subjectivist reading of Augustine is false insofar as it ignores Augustine’s general point that time is objectively dependent on accidental change predicated of substances. It is true, however, insofar as it makes important features of time(e.g., deictic time and flow) dependent on mental continuity. It is here that Augustine brushes up against contemporary physics.
Time in Modern Physics—A Crash Course
Turning our attention to the modern day, I claim that Augustine’s distinction between accidental change and mental continuity mirrors our contemporary distinction between “physical” and commonsense or “manifest” time.20 Indeed, the puzzles we currently face concerning how our science unintuitively represents the world are close to the Hellenistic debates that informed Augustine’s discussion. Attending to this similarity both rehabilitates Augustine’s conception of time and provides us with an example of how to respond to apparent conflicts between our theoretical concepts and commonsense notions. To see this, however, we first must understand something about modern physics and its unintuitive approach to time.
For ease of reference, let us call the conception of time given to us by our best science physical time and assert that Albert Einstein’s theory of general relativity is the best science in question.21 Einstein starts with the common assumption that we can locate events and objects in space by referring to a coordinate grid—much like the graphs with x and y axes that many of us are familiar with from high school.22 Depending upon where we start drawing our imaginary lines for these grids, we end up with different grids or frames of reference. So, for example, as I sit here typing we could imagine a three-dimensional grid in my office and then use that grid to locate the event of my typing by pointing to its coordinate along the x, y, and z axes. But to truly locate the event, we would need to add an additional axis, which we might call the t axis, to measure the time that an event occurred. Thus, the event of me typing this sentence could be located within this imaginary grid by locating its t, x, y, and z coordinates.
The principle of relativity states that the same general laws of nature apply to all frames of reference,and Einstein’s central insight in the context of this principle was that ifyou take the same general laws to apply regardless of the frame of reference, thenclassical physics contains a contradiction. To understand why, first imagine I am on a train. As I get up to walk to the dining car, I feel like I’m walking at a normal speed. We know, however, that these impressions are relative to my frame of reference inside the train car. If you were standing outside the train on an embankment observing me, then my walking velocity relative to the embankment would be the simple addition of the train’s velocity and my walking speed. Now imagine I am shining a flashlight on the train. From the perspective of the embankment how fast is the light traveling? Normally we would just add the velocities of the train and the light, but this leads to a contradiction. We know from independent experiments that light travels at a constant rate, unimaginatively labeled c. It cannot travel faster than c, even from a moving frame of reference, which suggests a contradiction between the classical mechanics of velocity and the well-supported claim that the speed of light is constant. The principle of relativity says that the laws of nature do not change just because we are in a new frame of reference, hence, we cannot avoid the contradiction by arbitrarily varying how the laws work. Einstein’s solution is to discard the hypothesis of classical mechanics that the time between two events is independent from motion. Put flatfootedly, given that light’s speed cannot vary we instead vary time.23
General relativity, generalizes these insights and models the way multiple frames of reference relate to each other within space-time, which is the collection of all frames of reference.24 This leads to some strange consequences, which are, Craig Callender recommends, best discussed by contrasting the manifest conception of time given by commonsense experience with the physical conception given by general relativity.25 Commonsense or manifest time includes things like order relations (e.g., events occurring at the same time as other events or occurring earlier or later than other events) and deictic structure (e.g., past, present, or future). Only some of these features, however, are modeled in physical time.26
For example, two spatially distant events happening at the same moment, what is sometimes called absolute simultaneity, have no physical analogues in general relativity. This claim is often misunderstood. We know that sometimes things appear to be simultaneous when they really are not.27 As I stare at the night sky this evening while sipping my coffee, I may see a star suddenly burn brightly as it bursts into a supernova. If we ask, “Did the event ‘sipping my coffee’ happen simultaneously with the event ‘bursts into supernova’?” it seems that intuitively the answer is yes. But of course, that is merely an illusion given that my location is billions of light-years away from the star’s explosion.
However, this mundane experience is not what concerned Einstein. Instead, he claims that after adjusting for the speed of light and relative distances, all notions of simultaneous events are dependent on the observer’s frame of reference. For instance, to an observer on Earth, two lightning strikes, one in Florida and the other in Paris, are simultaneous, whereas for an observer in a spaceship accelerating past Earth, these events could be ordered differently. This is not an illusion; instead, it is a feature of how time relates to the motion of different reference frames.28
Callender’s primary claim, which I affirm, is that whichever features are present in physical time are always interpreted by our mental faculties. This cognitive apparatus, which allows us to engage with both temporal order and apparent breakdowns of this order, provides clues to how our minds represent the external world.29 Therefore, if the phenomena of manifest time have no analogues in physical time, then we should ask what our cognitive apparatus is doing that gives rise to these phenomena As already noted, the notion of simultaneity has no physical basis in general relativity, and more dramatically, there is no deictic structure to physical time—there is no past, present, or future. As far as physics is concerned, there is no privileged now from which we can construe the flow of time. This is because no reference frame is privileged in Einstein’s theory—a reference frame that is later than the one in which I am typing this sentence is, from the perspective of physics, no less real.
This is the central question in contemporary philosophy of time. How do we make sense of the flow of time and its deictic structure if it is not present in our best physics? There are deep debates here, but for this essay I simply note that skepticism regarding the mind-independence of past, present, and future is not a recent consequence of our best science—it is present in Augustine too.
Augustine and Modern Physics—A Cognitive Conception of Time’s Flow
Contemporary philosophers, like Callender, approach the flow debate by asking why we have such a strong intuitive judgment that there is a universal now while rejecting a universal here? This point is worth lingering on Both here and now pick out a deictic center, whether in space or time, and so, Callender asks, why do we think that your here and my here can be distinct, such that neither is privileged, whereas now is universal?30
Callender appeals to the “hard facts of life,” by which he means the fundamental features of environments, biological structures, and human psychology.31 These features constrain our agency. Both a spatial here and a temporal now suggest perspectives centered on an observer, but they are distinct in that humans can rotate through space. Barring an obstruction, we can move through all spatial dimensions, and this agential power has no temporal analogue. We cannot rotate in time, and therefore, you and I cannot differ concerning the now. While I can shift an object on the desk from my right to my left, I cannot similarly shift the past into the present. Hence, when physics claims that space-time has no objective “flow” or privileged “now,” we intuitively, though mistakenly, disagree—it feels objective to us because we cannot change it.
This modern analysis mirrors Augustine’s claim that time’s “flow” requires us to “measure” against the continuum of our minds. Moreover, Callender’s argument that flow is primarily an experience of a change in us as an “updating ego” is similar to Augustine’s claim that the change metaphysically underwriting time involves properties “passing away” in the substance of our minds.32 As Matthew Wilcoxen summarizes, for Augustine “the soul ‘distends’ itself as it ‘engages’ itself and it is this self-activity that gives shape to our temporality.” This says more about agency than physical time. As Callender notes, with a very Augustinian phrase, “using memory or anticipation we can escape, backward or forward in time. But in terms of immediate experience we’re stuck in the same perspective.” He too argues that this explains the experience of “flow.” We conceptualize ourselves as moving selves because of our immediate experience and memories, from which we develop agential expectations, conjoined with the “hard facts” regarding agential power described above.33 Given this account, it seems clear that Augustine’s claim that mental continuity explains deictic time, but not objective accidental change, models well the distinction between “manifest time” and “physical time” in contemporary physics.34
I will conclude this section by noting a significant difference between Augustine and contemporary philosophers like Callender. For Callender, the conception of ourselves as selves moving through time is strictly an illusion—we are merely bundles of processes laid out across space-time like so many strings, with no objective selves to be found. In contrast, for Augustine saying that something depends on our minds does not make it unreal; it just makes it dependent, and this dependence underscores something important for Augustine. He claims at the end of book 9 that God is the “Creator of minds” who analogously “stretches out” God’s own divine life to uphold the objective time of the cosmos.35 This means that our limited experience finds analogy in God—the difference is that our upholding of time is predicated on the way things change and fade. And because changeable things tend toward nonbeing, we must “stretch-out” our soul to catch what fleeting impressions we can. Given Augustine’s account of evil as nonbeing, this suggests that he thinks deictic time is, in fact, fallen time.
And this opens a new avenue for theological exploration concerning what eschatological agency might look like—a conception of the life of the world to come that involves more agency and more movement, not less. For Augustine, redeemed time—present in Christand fully embodied in the eschaton—is still temporally marked change or movement, but the change or movement does not “flow”; it is not objectively deictic. Time becomes, for us, as malleable as space. The past is no longer faintly grasped by memory as it fades into nonbeing, nor is the future dimly seen through speculation, but instead they are always right at hand. In the eschaton, time and space are both right before me, and by reaching out, I can grasp either of them. Thus, our existence will no longer involve change-as-loss but rather change-as-movement.36
Reconciliation as Method
Careful attention to Augustine’s treatment of time reveals a nuanced theory that is both less subjectivist and more useful for addressing modern physics than critics have realized. Moreover, Augustine frames the question because of his intellectual milieu. Plato, Aristotle, and the Hellenistic schools provided the material out of which his Trinitarian passion built a comprehensive theology and philosophy of time. There is, I think, a larger lesson to be learned here for Christian philosophers and theologians.
Augustine models a synthetic project. He believed questions about humanity’s place in creation cannot be answered without engaging with the best intellectual accounts of his day. To engage with questions of time he therefore had to take up Aristotle’s antinomies, Plato’s account of eternity, and so on. But he did this for a theological purpose—exploring God’s relationship to nature. One way to capture Augustine’s philosophical method is to call it reconciliatory. A reconciliatory method recognizes that we are always already embedded in a host of seeming contradictions, and it resolves these tensions without losing the distinctive character of either side of the paradoxes.
Too often we respond to unsettling questions about humanity’s place in the universe by retreating into the cold comfort of reductive thinking. We claim our diverse experiences are reducible to something quantifiable and scientific—which, I note, is not often an attitude of scientists themselves. Or in contrast, we lapse into an incoherent parallelism, much like the two-books theology of the late Middle Ages, wherein we accept the book of experience as wholly separate from the book of science. This attitude is often taken up to avoid addressing the question of cosmic alienation or as a way of neglecting the hard work of taking our own intellectual and philosophical milieu seriously.
Both mere reduction and mere parallelism as intellectual methods are, I believe, unsatisfying. Augustine offers us an alternative. What would it look like, instead, to engage boldly with the very best science and philosophy of our time in a spirit of reconciliation? What would it look like if we, like Augustine, attempt to articulate humanity’s place in the universe with our feet firmly planted in the experiences of our time but with our eyes toward the movement of eternity?
- Russell, A History of Western Philosophy (New York, NY: Touchstone, 1945), 354; and see Jenson, Systematic Theology, vol. 2, The Works of God (New York, NY: Oxford University Press, 1999).
- I am following the lead of Jason W. Carter, whose illuminating paper “St. Augustine on Time, Time Numbers, and Enduring Objects,” Vivarium, no. 49 (2011): 308, I in many ways echo.
- Augustine, Confessions, trans. and ed. Albert Cook Outler (Peabody, MA.: Hendrickson, 2004), 242. For Plato and eternity, see Francis M. Cornford, trans., Plato’s Timaeus, ed. Oskar Piest (New York, NY: Liberal Arts, 1959), 15; and Plato, Timaeus 27c and 37c–38c. For Aristotle and eternity, see R. P. Hardie and R. K. Gaye, trans., Physics, in The Complete Works of Aristotle: The Revised Oxford Translation, vol. 1, ed. Jonathan Barnes (Princeton, NJ: Princeton University Press, 1984), 219a.15. For an extended argument about why we should take this interpretation of Plato seriously, see Callahan, Four Views of Time in Ancient Philosophy (Cambridge, MA: Harvard University Press, 1948), 22–23. For more on the role of successive and regular order in Plato’s models of eternity, see his discussion of generation and immortality in Symposium, trans. Robin Waterfield (New York, NY: Oxford University Press, 1994) 206e–209e.
- Augustine, Confessions, 244.
- Augustine, Confessions, 244 and 245. For a deeper discussion of the Hellenistic schools and their contributions to philosophy of time, see Pauliina Remes, Neoplatonism (Berkeley, CA: University of California Press, 2008); and A. A. Long and D. N. Sedley, eds., The Hellenistic Philosophers, vol. 1 (New York, NY: Cambridge University Press, 1987). Carter claims that commentators often go astray here, confusing Augustine’s ontological mode of argumentation in the previous chapter of the Confessions with his metrical arguments. Because of this, they interpret Augustine to say time only exists in the nonextended present, which then leads to the traditional subjectivist interpretation. I agree with Carter’s criticism. See Carter, “St. Augustine on Time.”
- Indeed, Augustine’s presentation of the paradoxes of measuring time follow Aristotelian considerations almost exactly, though without adverting to Aristotle’s substratum/being distinction (see Augustine, Confessions, 246–47). Stoic philosophers further build upon this Aristotlean terminology, calling it the subsistent/existent distinction.
- It is worth noting the similarities between this concern and the concern of how we measure the motions of bodies found in Aristotle. See Physics 219a.10–219b.30. At this point in the dialectic, Augustine rejects two views that correspond to Neoplatonic and Aristotelian positions. The first is that time consists in the motion of heavenly bodies. The second is that time consists in motion as such. He argues that time, since it is measured and since by it we measure other forms of motion, must be extension (see Augustine, Confessions, 252, 253, 255, and 256–57). A more explicit statement of this belief is found in Augustine’s De musica wherein he states, “nothing extended in time and space is large by itself alone, but only relatively to something smaller, nor is anything small, except relatively to something larger”; W. F. Jackson Knight, St. Augustine’s De Musica: A Synopsis(Cambridge, UK: Severs, 1949), 97; also see Augustine, De musica 6.7.19.
- Augustine, Confessions, 254–55.
- The language Augustine uses for “extendedness of the mind” (distention animi) evokes the Neoplatonic doctrine found in Plotinus among others. The locus classicusfor these arguments is found in Plotinus, The Enneads, trans. Stephen MacKenna (New York, NY: Pantheon Books, 1960). It is well documented that Augustine was familiar with Neoplatonic philosophy, but an underdeveloped area of inquiry is the extent to which Augustine had access to Aristotelian ideas (see Carter, “St. Augustine on Time,” 317). Certainly, the relationship between time’s measurability and its existence, a relationship considered by Aristotle, haunts Augustine’s arguments for the “measurement in the mind” thesis, but Augustine did not, as far as we know, have access to any of Aristotle’s major works on natural philosophy (such as the Physics). Carter suggests that Augustine shows some familiarity with Aristotelian ideas through Neoplatonic mediators such as Porphyry, Plotinus, Ambrose, and Marius Victorinus. Aside from these philosophers, it is likely that Augustine had access to paraphrases and perhaps even direct translations of some of Aristotle’s other works. For example, earlier in the Confessions, Augustine says he has read “a book of Aristotle’s entitled The Ten Categories,” so some acquaintance of Aristotelian ideas should be expected (see Augustine, Confessions, 70). There is disagreement as to whether the text Augustine refers to here is Marius Victorinus’s complete translation of the Categories or just a Latin epitome, probably the so-called Paraphrasis Themistiana. Carter considers these options in “St. Augustine on Time,” 317, especially footnote 52. All of this suggests that one part of the traditional view—that Augustine’s theories are a radical departure from earlier thought—is false.
- Augustine, Confessions, 255–56.
- Augustine, Confessions, 256.
- Carter, “St. Augustine on Time,” 310, 310, and 312.
- Augustine, Confessions, 242–43.
- Augustine, Confessions, 249.
- Carter, motivated by his arguments against the traditional view, denies that these operations of the mind are times at all but rather the epistemic effects of objective change. I disagree, as noted, because this trivializes a crucial feature of much of late antiquity and medieval thought, namely, that there is a close connection between what we perceive and “real” objects. Just because something “depends” on a feature of our minds does not mean it is not “real” in some sense of that word.
- Augustine, Confessions, 257 (italics added) and 267. The latter quote occurs in a discussion of the unformed and chaotic abyss over which God’s spirit moved, which gives us an example of disordered “change” without time. Hence, it is only a certain change that is to be understood as temporally ordered.
- Augustine, The City of God, trans. Marcus Dods (New York, NY: Random House, 2000), 350. Italics added.
- See Carter, “St. Augustine on Time,” 316; and Augustine, The Trinity, trans. Stephen McKenna (Washington, DC: Catholic University of America Press, 1963), 183–85.
- See Carter, “St. Augustine on Time,” 318. This harkens back to the point I raised earlier concerning the necessity of change relative to a continuity for time to exist. According to Augustine’s philosophy of time, it seems that the relevant continuity is substance.
- This terminology is taken from Craig Callender, “Time Lost, Time Regained,” November 28, 2016, 1–4, https://docs.wixstatic.com/ugd/b2eedd_0748138230344a0797681fe1b706f36b.pdf, now included in Metaphysics and Cognitive Science, eds. Alvin I. Goldman and Brian P. McLaughlin (New York, NY: Oxford University Press, 2019), 17–37.
- Of course, calling general relativity our “best science” and claiming that it gives us an accurate conception of time are both controversial claims in metaphysics and philosophy of science, but I aim to show Augustine’s salience for our contemporary situation. As such, assuming that the standard view is correct or close to correct is justified. To go further, I would point a skeptic to the monumental predictive success of general relativity as a strong (though defeasible) reason to take general relativity to be on the right track. The term general relativity is used because it concerns the application of the relativity principle to all frames of reference, whereas special relativity applies the relativity principle only to “uniformly moving coordinate systems devoid of rotation.” General relativity also incorporates gravity in a crucial way that I largely ignore for the purposes of this paper. For more on general relativity, see Einstein, Relativity, trans. Robert W. Lawson (New York, NY: Barnes and Nobel, 2004), 53–91.
- For Einstein’s use of a coordinate grid to discuss the location of events and objects in space, see Relativity, 3–8.
- Einstein, Relativity, 27. The same implication of the relativity principle—that time-intervals constrict or dilate depending on the moving frame of reference—is also true for space-intervals, which is why in relativity if an object moves fast enough, it will “stretch” or “constrict” depending on the frame of reference. Since this essay is about time, I ignore this consequence—I should note, however, that the conjunction of both time dilation and spatial distortion are strictly necessary to avoid certain paradoxes. Likewise, to streamline the argument that follows, I have elided many other details. For example, the standard speed of light, c, is really the speed of light when no intervening factors are in play, which complicates the thought experiment slightly. Moreover, general relativity is not merely the generalization of special relativity; it also includes considerations of acceleration and gravity that are not a part of special relativity. The reader should, as a general rule, consider everything to be more complicated than this brief gloss will allow.
- We can now visualize this picture of reality. Picture space-time as a coordinate system, where the x axis and y axis represent three-dimensional space as a plane, and the z axis represents time (call it the t axis, for simplicity). A single event is a point within this coordinate system. We can model the light both coming from and arriving at a given event. We also know that if light were uniformly emitted from a single point (imagine turning on a bare light bulb), it would race away from that point in all directions, making a sphere with an edge expanding at the speed of light. Since our model represents three-dimensional space as a two-dimensional plane and since light travels at a constant speed when other factors are not at play, we can trace a cone shape across the t axis to model how the sphere of light expands. Note that there is objective ordering in the model. I will experience the first event, e1, as coming earlier than the second event, e2. Similarly, you will experience e3 as happening earlier than e4. In contrast, because you and I are greatly separated in space in the model we cannot compare the order of events between our frames of reference, so e2 is according to physics neither before nor after e4.This unintuitive fact reveals one way in which our manifest conception of time is often at odds with the physical conception of time given in general relativity.
- Callender, “Time Lost,” 4–5.
- For example, suppose I attend a concert. The band starts with their most popular song and then later plays a more obscure track. I would make the judgment that the popular song came earlier than the obscure song. This objective ordering of events is represented in general relativity by saying that events that are merely separated across time but that can be causally connected in space still have objective temporal ordering, which is to say our that commonsense “earlier/later” distinction is modeled even within physical space-time. Of course, “causally connected” is defined in a manner that would give some philosophers pause. Strictly speaking, two events are causally connected in general relativity if the time separation between them is less than their spatial separation (i.e., the distance) divided by the speed of light. This makes sense within the theory, but there is some philosophical question about whether this sort of connection is best understood as “causal.” Also, as already noted, general relativity does more than merely generalize from special relativity; it also extends Einstein’s insights to accelerating objects and gravity. For the purposes of this essay, I ignore these other considerations. Furthermore, I am eliding many metaphysical, physical, and terminological difficulties here concerning the nature of this collection of frames of reference. For example, space-time is sometimes referred to as the manifold, for reasons that are both intuitively obvious yet technically complicated. As such, I will stick to the terms I’ve already introduced—frame of reference and space-time—for the sake of simplicity.
- For example, since light is the speed limit of the universe, it is the upper limit of information propagation as well. This means that if, from the perspective of a particular observer, an event falls outside of this limit, it is necessarily unobservable from that perspective until the light intersects. This is why when we look at the stars at night we are looking into the past. The spatial separations between events are so great that once the light of the star reaches us, it is billions of years old.
- The reason for this result may seem obscure, however, it is yet another consequence of the invariability of light’s speed. To see why, consider a famous thought experiment on the relativity of simultaneity that was originally from Einstein but has been adapted with animations in John D. Norton, “Special Theory of Relativity: Relativity of Simultaneity,” Einstein for Everyone, 2018, https://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/Special_relativity_rel_sim/index.html.
- As Callender notes, “Our cognitive and perceptual architecture often gets it ‘wrong’ (shifts an information stream), to get it ‘right’ (recover the objective spatiotemporal map)”; Callender, “Time Lost,” 6.
- Callender “Time Lost,” 12.
- Callender, “Time Lost,” 13.
- Although few have connected Augustine’s account with contemporary cognitive science and time’s “flow;” the broader insight that Augustine’s arguments in Confessions are still useful for discussing time’s “movement” and its “interconnectedness” have been noticed by a few. For a very intriguing theological interpretation that comes to similar conclusions, though perhaps without giving Augustine enough credit, see Jeremy S. Begbie, Theology, Music, and Time (New York, NY: Cambridge University Press, 2000), 71–97.
- Matthew A. Wilcoxen, “Augustine’s Theology of Time: A Trinitarian Reassessment of Confessions 11,” Heythrop Journal 57, no. 4 (2016): 668; and Callender, “Time Lost,” 13 and 14–15.
- There is, however, an important difference here. Namely, for Augustine it seems that objective change does involve a genuine coming to be and passing away of properties predicated of a substance. This is different from many contemporary philosophers who think that the future and past do exist, but that they are temporally distant from me right now. So all change is better conceived of as a latter temporal part of ourselves or the space-time manifold. I do not engage with this complex topic here, but it should be noted that to fully apply an Augustinian approach to time to contemporary issues would require exploring this difference.
- Augustine, Confessions, 258–60.
- Wilcoxen’s “Augustine’s Theology of Time” is an invaluable resource for thinking through Augustine’s distinction between fallen and redeemed time.