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Presentism vs. Eternalism: What Relativity Has to Say

Paper Type: Free Essay Subject: Physics
Wordcount: 5058 words Published: 8th Feb 2020

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This paper aims to establish that arguments which seek to use relativity theory to endorse any form of eternalism or four-dimensional space-time “blocks” of reality are inherently mischaracterizing relativity. It is argued that attempts like Putnam’s (1967) are especially misguided if one attempts to use a combination of classical presentism and special relativity STR to support eternalism, as the former is precisely what the latter rejects. The paper proceeds as follows: §1 will provide a summary and analysis of Putnam’s argument. It will be argued that the argument fails to establish the desired conclusion as two of its premises mutually exclude each-other. §2 explores an implicit assumption in Putnam’s argument; that events in the future of one world-line are capable of being simultaneous with another world-line. It will be shown that a spatialization of time, however common, is a mischaracterization of the fusion of time and space under relativity. Finally, §3 will attempt to provide a more accurate description of what relativity implies for the dialectic in the metaphysics of time.


Putnam’s argument starts off with what he calls the “man on the street’s view” of time; that all and only things which exist now are real. He then makes a few uncontroversial assumptions which take him from the initial postulate to the conclusion that all things past, present and future are real. (NB: the argument only ‘proves’ some future things are real, but he states that it can easily be generalized to all future and past events.) The argument reads like a simple reductio ad absurdum, in which the conclusion is obviously absurd and should have led us to reject the initial postulate. However, he explicitly states that “the problem of the reality and determinateness of future events is now solved” (p.247). This leads us to believe that he takes the conclusion to be a valid inference from the assumptions and one that we should adopt in our ontology. A summary and analysis of his argument will be sketched out below.

Initial postulate: All and only things which exist now are real.

His argument proceeds by utilizing these further assumptions:

(i)                  I-now am real

(ii)                There is at least one other person (you-now) that is also real

(iii)              You-now may be in relative motion to me

(iv)              There are no privileged observers NPO – this is construed as: If all and only the things that stand in a certain relation R to me-now are real, then it is also the case that all and only the things that stand in R to you now are real.

(v)                Special Relativity STR

He states that under classical physics, if R is taken as the relation of simultaneity then under the initial postulate, (iv) is satisfied because R is transitive. i.e. if event a is simultaneous to me-now and me-now is simultaneous with you-now, then a is simultaneous with you-now. However, under STR (v), if me-now and you-now are moving at relative velocities to each-other (iii), then our “now’s” will not coincide. Thus, I cannot take simultaneity-in-my-co-ordinate system CS to be the absolute R without violating NPO (iv). He states that STR requires us to reformulate R to mean ‘simultaneity-in-the-observer’s-CS’ (R1). Although a little vague, I take him to be stipulating that ‘the observer’s CS’ to mean any observer’s CS at the given time and location. Since you-now and me-now are simultaneous at a point and therefore simultaneous in all CS’, then under the new relation R1, if me-now is real, you-now are also real. But if you-now are also real then everything simultaneous-in-your-CS is also real. While things in my future cannot stand in R to me-now, they can stand in R1 to me-now and this is the relation we must take in order not to violate NPO. He states that if we want to preserve half of the initial postulate; (2) all things that exist now are real, then if I assert 2 in reference to R in my CS, which includes you, and you assert 2 in your CS, which includes events in my future, and R1 holds between “all events on some simultaneity line in any observer’s CS and them at-the-appropriate-time” (p.243), then events in my future in virtue of R1 will be real according to me-now. An example to illustrate this: If event a and b are simultaneous to me-now Rab, and events b and c are simultaneous to you-now Rbc, and if you-now and me-now are absolutely simultaneous in any CS, then we cannot use Rab nor Rbc as an absolute relation of what exists, we need to use R1 which includes all events a simultaneity line in any observer’s CS: Rabc. However, event c in virtue of not being on my simultaneity line lies in my future and if Rabc is an expression of everything that exists now then my future is real relative to me-now. Thus, not only events which I consider to exist now in my CS to be real but all future events are also real, provided it can be formulated by a transitive R1 in any CS. From this he concludes that all events past, present and future are real.

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I will argue that the argument misses its mark in several ways. Firstly, he gives no evidence of why we should believe the initial postulate. Second, the initial postulate is exactly what STR refutes. Although it is not explicitly stated, I will assume that Putnam assumes the classical picture of a succession of instantaneous three-dimensional plane of spatial coordinates moving in one dimensional time, with each one of these instantaneous cross-sections being what exists now, replaced by another that exists now, and so on ad infinitum. To see why this is rejected by STR, a brief history is in order. STR was sparked by the dispute between absolute and relative motion, which directly challenged the concept of absolute space. The concept of aether was postulated to distinguish which dynamically equivalent system (Galilean relativity) corresponded to absolute space (if it were to exist). The Michelson-Morley experiment was conducted to detect the aether-wind which was postulated to exist in virtue of the earth moving through absolute space. The null result (of the speed of light varying depending on the placement of the apparatus in the direction of the movement of the earth and against) signified the end of both the aether theory and absolute space (Einstein & Infeld, 1938). Lorentz-Fitzgerald, in an ad-hoc attempt to save the theory of the aether and absolute space, proposed that the null result was due to the fact that dimensions of moving bodies contract when parallel to their motion, whilst perpendicular dimensions remained constant (Capek, 1961). They proposed that the constancy of light in vacuo c was apparent due to the real contractions of the Michelson-Morley apparatus. STR utilizes the null result of the Michelson-Morley experiment – which Einstein interpreted as c being absolute – combined with Galilean relativity to reach the conclusion that both time and space are relative, and contra-Lorentz-Fitzgerald, renders both length contraction and time dilation as apparent (only observed from different CS and always reciprocal). The most significant result in the metaphysics of time comes with STR’s rejection of absolute simultaneity. 

In the Classical picture of the four-dimensional spatio-temporal continuum, touched on previously, instantaneous material configurations (of the three dimensional spatial ‘plane’) move successively in the one dimensional time continuum. One of these instantaneous cross sections symbolizes the present state of the universe. All points contained in this cross section are simultaneous in an absolute sense. This intimate relationship between the two concepts of absolute space and absolute simultaneity can hardly be more clear. If space is a juxtaposition of points, then all points co-exist, i.e. simultaneously and never in succession. It seems quite clear in virtue of STR’s history and its explicit denial of absolute simultaneity, there is a parallel rejection of such instantaneous cross sections of absolute space. We can already start to see why Putnam’s initial assumption of the “man on the street’s” view of all and only all things that exist now are real should be questioned. If his notion of now is taken to be the instantaneous cross section of absolute space (represented by a moment in time), it is already denied by STR.

On Putnam’s reading, under STR, we cannot distinguish whether my instantaneous cross section is the real now or whether yours is, so by transitivity of the new relation R1, all events that lie in either of our different cross sections are real. However, it is not the case that STR denies me prioritizing my cross section over yours, it is that there are no instantaneous cross sections simpliciter. They are “artificial carvings” which are embedded in the dynamic spatio-temporal continuum (Capek, 1961). We will see this more clearly in the merging of space and time discussed in §3.

We may now consider the possibility that the above reading of Putnam is not the most charitable reading or that it may be a mischaracterization of what the argument is actually trying to say.  Stein (1968) muses on “what sort of argument contradicts its own premise?” (p.17) when comparing the outcome of the initial postulate – that all and only things which exist now are real – and the conclusion of Putnam’s argument – that all things past, present and future are real. Stein concludes that Putnam’s argument is a sort of heuristic argument, agreeing that from a purely deductive point of view, the argument should have been a reductio. A heuristic argument, he states, is one where the conclusion of an argument corrects its premises. Putnam’s argument seems to refute the initial premise, then arrive at the desired conclusion from saving one half of the view (2. Above) whereby what exists now is real. Stein notes the arbitrariness of this and wonders why we want to save this half and not the converse – i.e. only things that exist now are real. This route combined with STR would have implied the opposite of everything being real, namely, that for any event, it and it alone is real. He further states that Putnam’s formulation of the principle of NPO merely requires R1  to be an equivalence relation. But under the Einstein-Minkowski formulation of space-time, there are no intrinstic partitions into any equivalence classes besides the one into all of space-time and that into a single point. Both are trivial and reflect Putnam’s conclusion and the conclusion of the half of the initial postulate not saved, respectively.

It seems either way, we should not be convinced of taking seriously Putnam’s conclusion in our ontology. So far, I have argued that Putnam’s argument which should have been a simple reductio, misses its mark in several ways if he is actually trying to establish the conclusion that all things past, present and future exist. Not only does he provide us with no evidence of why we should accept the initial postulate, any attempt to use STR in conjunction with it is seriously misguided, as the initial postulate is precisely what STR rejects. The effort, construed this way, would be as absurd as starting from the initial postulate that color is an intrinsic property of objects and pairing that with the discovery that colors are different wave-lengths of light reflected off certain surfaces to conclude that wavelengths are intrinsic properties of objects. No argument can succeed with two of its premises being mutually exclusive of one another. I have further explored the possibility of a mischaracterization of Putnam’s argument, and considered it one in which it is construed as a heuristic device to correct its premises. However, the attempt to reconstruct the initial postulate to save one half of it is completely arbitrary – there is no reason why we should want to save that half and not the other. Either way, we should not be taking Putnam’s conclusion as any concrete resolution to the determinateness of the future, especially not one that STR endorses. The next section will explore an implicit assumption of Putnam’s argument, namely that an event in my future is even capable of being simultaneous with another observer’s world- line.


The impossibility of separating time and space was clearly formulated by Minkowski in 1908. Although (mathematically) implicitly implied by the Lorentz transformation. What sparked what Capek calls the ‘fallacy of the spatialization of time’ was potentially in Minkowski’s use of the term “the world” when referring to the 4D continuum of point-events, mistaking a dynamical unfolding process(es) for a completed whole. Further, our own experience or inability to perceive really fast or really slow motions may have contributed to the fact that we reduce unobserved motion to different positions at different moments. i.e. the sun moving across the sky or inferring the motion of a bullet from barrel to target. Due to this, it was considered completely adequate to consider time as the fourth dimension of space whereby past, present and future are juxtaposed like the points in space, rendering the concept of becoming to one of being. This can be seen in Putnam where he implicitly implies that an event which is in my future, already exists (for there can be no non trivial argument over whether something can be “real” if it does not already exist). According to Einstein, this tendency to spatialize time is a misinterpretation of relativity (Capek, 1961). The spatial symbolization is dangerous as it leads us to neglect an essential difference between succession and juxtaposition, reducing past, present and future to differences of position. Things cannot be truly successive if they co-exist. Recent attempts to explain the “illusion of succession” from static juxtaposition faces difficulties as the animating system – which must be a process – must arise somewhere. To reduce it to the mental, I suggest, is an unattractive route, unless we are to regress back to cartesian dualism of the mind, for any physicalist interpretation of consciousness will reduce the mind to the same static relations. However, it is not the aim of the paper to discuss these issues. Coming back to STR, it seems apparent that the relativity of simultaneity is the most convincing argument for this static interpretation. If there are no absolutely simultaneous events and succession may be reversed in one CS compared to another then there is no objective status that can be attributed to time or succession. However, STR does not rule out absolute succession in causally related events, thus the world lines are irreversible, for no effect can occur before or simultaneous to its cause – as the speed of light is also the limit for causal relations. Further, this irreversibility is absolute for any CS. Therefore, while absolute space, thus absolute juxtaposition of events is never absolute for all observers, certain types of succession are absolute in all CS’.  Surely, since absolute space and juxtaposition are denied whilst certain succession (while metrically variable – i.e. time dilation under the general theory of relativity GTR- but always topologically invariant) and thereby asymmetry are preserved shows the priority of time over space. It may be interesting to note that Einstein himself refers to the fusion of space and time as “time-space” (Einstein & Infeld 1938).

Capek argues that instead of a spatialization of time, we should rather construe relativity as endorsing a dynamization of space. Since both concepts are so intricately intertwined under relativity, it is not proper to treat space as an independent entity, but we must also realize how much it has transformed from the classical conception. Distance and succession may no longer be considered mutually exclusive. Recall that absolute instantaneous cross sections of the material configurations of space were denied (§2). Thus, distance between any two points may no longer be instantaneous. To admit this would be to revert to the notion of absolute simultaneity of distant points, which STR explicitly rejects. There is some inherent difficulty in accepting the rejection of successive causal connections occurring in space and the instantaneous geometrical connections constituting space itself. However, if we are to truly accept relativity, we must accept that the only links in nature are chronogeometrical, not purely geometrical. Capek summarizes in one sentence, “concrete physical processes do not need any static container.”

This is more evident in GTR where not only time and space are fused, but matter is thrown into the mix. Under GTR, there is no relation of causality for the warping of space by matter, the relation is one of identity (Einstein & Infeld 1938). Thus, relativistic time-space does not have a rigid structure, curvature not only varies from place to place but from one time to another. Not only is there a continuous local change of curvature but the total curvature of space-time varies in time. This is evidenced by considerable astronomical evidence for the expansion of time-space, i.e. the continuous increase of the radius of curvature (Capek, 1961). This, I believe, instantiates a radical incorporation of the (classical) concept of space into that of becoming.

No longer can we speak of points in space as a pre-existing “track” that material contents may occupy successively at different times. Motion in space is only possible pre-relativity. Bertrand Russell (as cited in Capek, 1961) gives a clear illustration of what this means. He states that pre-relativism, it was entirely plausible to think that positions in space exist creating a path which motion follows, one that would remain before and after the motion. The example he uses is a tram moving along a pre-existing track. However, this is no longer tenable as a moving point is a series of points in time-space. A later point cannot pursue the same “course” since it will have different time coordinates. A simpler illustration is thus: I walk from my house S1 to the university S2 in a certain time frame say t1. My room-mate then walks from S1 to S2 at t2. We are not right in assuming that we have crossed the same spatial points S1 – S2 at different times, as from the perspective of the sun, the spatial routes between S1 and S2 changes with time. I.e. the earth is moving. Relativistic space changes with its dynamic physical content. It is absolutely crucial that we relinquish the container view of space if we are to get a clear understanding of time under relativity. As soon as we begin to chart the motion of matter, we begin to plot the future positions of its future “path.” We must not forget that in virtue of their futurity, these points do not exist, risking transforming potentiality into actuality. The compromise of stating that although the positions exist, they are not yet occupied is also untenable. This distinction between the spatial container and motion means that while succession is assigned to motion, it is completely disconnected with space, which is not viable in relativistic time-space.

In light of what has been shown, we see further inadequacies in Putnam’s assumptions. Not only do neither of the relations me-now-a-b and you-now-b-c exist, but the further space-like each event is to another, the larger time-like apart they are. So while it may be true that you-now is absolutely simultaneous to me-now if we are at the same location, the relation R1abc is not possible if they are causally connected, as causal succession must be absolute in every CS. But if they are far apart enough to not be causally connected, then they can be in no way simultaneous with one another.

This section has explored one of Putnam’s implicit assumptions, that all events, past, present, future pre-exist (but does not exist “now”). I have attempted to show that this spatialization of time is a misinterpretation of the fusion of space and time. Given the priority of time over space in relaivity, we should instead view the fusion as a dynamization of space. The final section explores what I believe to be the actual implications of relativity for the metaphysics of time.


What I have attempted to show above is that although there is no universal distinction of a present if the present is formulated in the classical sense of an instantaneous cross-section of material configurations in absolute space, there is also no reason to adopt an eternalist frame of a static, pre-existing four dimensional world. Rovelli (2018) notes that the idea of the universe existing now in a certain configuration that changes together in succession doesn’t stack up anymore, however, just because the world cannot be ordered in a single, linear file doesn’t mean there are no relations at all. He utilizes an example of Genealogy to show how, even though a complete universal wide ordering isn’t possible, there is still a partial ordering of the world.

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On a normal ordering of Genealogy, we would separate each generation of parents and children. I.e. my grandfather and grandmother are of a generation, my mother and father, myself and my siblings, then our children etc. But consider a case (In ancient times, where I guess incest was less taboo) whereby a woman D has a child E with a man B, where B is the brother of C, who is D’s father, and both B and C are sons of A. i.e. the woman married her uncle.







There is a close parallel in Fig.1 above and the temporal structure given by relativity, it makes no sense to ask whether B is in the same generation as C or D because there is no single concept of generation. i.e. the rejection of instantaneous cross-cuts representing the “present”. There is an order established between humans but not any humans. If B and C are in the same generation because they have the same father, then B and D will be in the same generation because they have a son. But this would necessarily force the absurd outcome of placing D and her father C in the same generation. So, while partial order is established (B, C and D absolutely come after A and before E) it is meaningless to say whether B and D or B and C are before or after one another. To put it more precisely; an order of Before and after are established for any forebearers and descendants but not between everyone. i.e. the familiar notion of linear time may exist for each world line, or in the analogy, between A, B and E and again for A, C, D, and E, but any attempts by either “world-line” to generalize this universally is doomed to failure. The parallel here is that, just because we cannot have a universal, linear ordering of instants, does not mean all events exist at the same time, or that any ordering bears no meaning. This would be as absurd as saying that because we cannot absolutely establish the order of succession between B, C and D, we must think that A, B, C, D and E co-exist together.

Although relativity negates instants of time, it does not remove contemporaneous intervals of time, i.e. the interval between A-B-E is contemporaneous with A-C-D-E. We can see this in Langevin’s travelling twin experiment – whereby one twin jets off on a rocketship travelling almost of the speed of light, returns to earth to meet the other twin, younger – shows that although they experience different “times” they leave from the same “point in time-space” and return to meet another at a different “point in time-space.” This shows that the two time series must be contemporaneous in the same stretch of universal duration. Otherwise, they would not be able to meet back up. The topology remains the same, whereby the setting off is succeeded by the meeting back up. These two “points,” which are on the same worldline, are absolutely successive and irreversible, as shown in §2. This led whitehead (as cited in Capek, 1961) to differentiate what he calls the universal creative advance of nature from the various manifestations of discordant time series’. For ease, I will rename this creative advance a universal becoming. Whitehead notes that this universal becoming is not properly serial and cannot be reduced to any one time-series, nor is it appropriate to generalize from any time-series into a universal linear time series. The single time-series’ are only used for measurement and as such, are abstractions from what they are measuring. These each measure some aspect of the universal becoming and the entire collection of them express the properties of the becoming that are measurable. Similarly Bergson (as cited in Capek, 1961) states that relativity does not destroy the unity of “real time” but presupposes it, for what would it mean to say that [each time series] is contemporary without this unique and experienced duration.

As matter is “resorbed” so to speak into space-time, it should follow that the traditional account of concrete physical processes must also not be distinct from time. Time, by virtue of its merging with its material content loses its classical properties of homogeneity and uniformity. The relativity of measurement dependent on different curvatures of the gravitational field under GTR falls out as a natural consequence of this. However, despite the metrical diversity in each time series, each remain topologically invariant and enter into relations of contemporaneity with each-other and thus constitute the universal becoming that is reality. This contemporaneity replaces simultaneous spatial juxtaposition in the synthesis of time and space under relativity.

Concluding remarks

This paper has argued that Putnam’s argument, which construed deductively, should have been a simple reductio ad absurdum, misses its mark in several different ways if he tries to establish the actual reality of the conclusion he reaches. This is especially misguided in his attempt to utilize STR in support of his conclusion as his initial postulate is exactly what STR denies. An alternative reading of the argument as a heuristic device does not make either his conclusion that everything past, present and future are real any more convincing nor does it achieve its heuristic-goal for a revision of the initial postulate to save one arbitrary half of it. I have further explored an implicit assumption in his argument, one which I believe is commonly extracted from STR, that a fusion of space and time implies that all events pre-exist in a ‘block-universe.’ I have attempted to show that this is a mischaracterization of relativity and that we should instead view this fusion as a dynamization of space over a spatialization of time. Although STR explicitly rejects the classical view of presentism, it by no means endorses eternalism. I have hoped to show that the actual implications of relativity for the dialectic in time is that our familiar notions of a linear, universe-wide ordering of events is no longer adequate. However, a partial ordering is retained, along with irreversibility of world-lines which entail asymmetry. Just because a succession of instantaneous material configurations of space is denied, does not imply that all succession is denied. The world can still unfold despite not unfolding in a neat linear fashion. Contemporary physics has not only merged time and space together but also matter and process. In light of this, time cannot be separated from its material processes. Troubles arise when we attempt to retain classical notions of time and space and match that with new developments in physics. Any successful, ‘non-abstraction’ conception of time must relinquish the familiar notion of a distinct linear ordering of instants and embrace the nested, overlapping ‘universal becoming’ that is reality.


  • Capek, M 1961, ‘The Philsophical Impact of Contemporary Physics,’ Van Norstrand, New York
  • Einstein, I & Infeld, L 1938, ‘The Evolution of Physics,’ Cambridge University Press, London
  • Putnam, H 1967, ‘ Time and Physical Geometry,’  The Journal of PhilosophyVol. 64, No. 8, pp. 240-247 
  • Roveli, C 2018, ‘The Order of Time,’ Riverhead, New York 
  • Stein, H 1968, ‘On Einstein-Minkowski Space-Time,’ The Journal of Philosophy, Vol. 65, No. 1 pp. 5-23 


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