Philosophy and Science: Continuity or Discontinuity? Presentism Meets Physics

Malcolm Pollack writes,

 

I hope you'll forgive me for hammering you with emails, but I just wanted to thank you for inviting me to join you in giving this paper a careful going-over. [Christian Wuetrich, "The Fate of Presentism in Modern Physics" in New Papers on the Present, Philosophia Verlag, 2013, 91-131. ] It has given me, as a civilian, yet another opportunity to appreciate the care and attention to detail that professionals in your field must bring to their work. I was struck in particular by this paragraph, from section 3:

 

  "The acceptance of a conflict between presentism and not only SR [Special Relativity], but all of current, as well as prospective, fundamental physics paired with an insistence on presentism amounts to a rather comprehensive rejection of physics. It thus fundamentally contravenes naturalism, a venerable tradition going back at least to Aristotle. According to naturalism, philosophical—and metaphysical—inquiry is continuous with scientific inquiry. To be sure, naturalism is not a logical truth—it is a substantive philosophical thesis. But it is one whose defence has to wait for another day; for present purposes, I simply assume a minimal naturalism which demands that no philosophical thesis be in manifest contradiction to facts established by our best science. Restricting this weak thesis to metaphysics, it can be translated as necessitating that the physically possible worlds are a subset of the metaphysically possible ones, for if the metaphysical theories were in contradiction to the physical ones, then there would have to be some physically possible worlds (and perhaps all) which are metaphysically impossible, as for the metaphysical theory to be incompatible with physics, it would have to rule out some physically possible worlds as impossible. In other words, metaphysics would a priori deem impossible what physics affirms is possible. Assuming that all physically possible worlds are also logically possible, I see little justification for disavowing this weak form of naturalism." 

 

I find this precision, clarity, and style delightful entirely on its own, quite apart from any conclusions it may be leading to. Much obliged.

 

Malcolm,

 

I thank you in return for giving me the opportunity to achieve clarity on these topics in connection with a book on metaphilosophy I must finish before the Grim Reaper (Benign Releaser?) lops my head off.   As a chess player you know what it is like to be in time trouble with Sudden Death looming, except that it this case it is a scythe and not a flag that will fall.  And what the fall will end won't be a mere game.

 

I will begin by listing some of the main points in W's article, clarifying the key terms, and formulating some of the issues that arise.  Ask any questions or make any objections that occur to you. If you find anything I say less than clear, say so.  Double quotes mean that I am literally quoting the author. For all other purposes I use single 'quotes.' (One of those uses is instanced in the immediately preceding sentence.) Numbers in parentheses are page references.

 

1) The author is committed to thinking of time as spacetime, a four-dimensional manifold M composed of "points."  (92) These are spacetime points or temporal locations specifiable by x, y, z, and t coordinates, where a spacetime point is a punctuate (duration-less) instant.  I take it that M is a continuum so that, between any two instants, or temporal locations, there are continuum-many (2-to-the-alepth-null) instants or temporal locations. This assumes Cantorian set theory and the actual (as opposed to potential) infinite.  But then  on the same page, he speaks of "events."  As I see it, an event is not the same as the time(s) at which it occurs.  (The occupant of a spatiotemporal location is not the same as the location it occupies.) I should think that there are times when nothing happens, i.e., when no event occurs,  but that whenever an event occurs it must occur at a time or over times.  The same goes for spacetime points. Some are unoccupied by physical events, no? An event that is not punctuate like an instant I call  a process, even it it lasts only a nanosecond. Nanoseconds and related terms pertain to the "metric" which applies to M. (92)  An example of a process, i.e., an extended event, is a storm or a melody.  A side point worth pondering is that the universe, supposing it began to exist with a Big Bang, could be metrically finite (12 or so billion years old) despite M's having the cardinality of the continuum, which implies that there are continuum-many events/times between now and the Big Bang

 

One of the issues that arises here, one not discussed by W., is whether concrete things such as the piano on which the melody is played can be "assayed" (technical term of Gustav Bergmann with mining provenience) as extended events or processes. If so, then pianos and piano players have temporal parts in addition to spatial parts -- a view vehemently denied by many philosophers.  A melody is not wholly present at every time at which it exists; is the same true of Billy Joel? Melodies and storms unfold over time; they have phases. Do persons unfold over time? Is a person a diachronic collection of person-phases? A person persists through time, no doubt -- 'persists' is a datanic term  in my lexicon -- but does he persist by enduring or by perduring? Is a person or a concrete thing/substance wholly present at every time at which it exists or not? This question goes to the back burner.

 

2) Given the fundamental presupposition that time is in reality spacetime, eternalism and presentism are defined by the author as follows. Eternalism is "the position claiming physical existence for all events in M," whereas presentism "partitions events into past, present, and future events" together with the proviso  that only the events belonging  to the present partition enjoy ontological privilege. (92) "Thus the sum total of physical existence is a proper subset of that according to the eternalist." (92)

 

This I find less than clear. What does the author mean by physical existence? As opposed to what? Surely not mental or abstract/ideal existence.  Does he mean the existence of events at times, as opposed to the times at which they exist?  An event is not the same as the spacetime point or points at which it occurs.  Is it not obvious that the occupant of a location, whether spatial or temporal or spatiotemporal, is not the same as the location? A location exists just as well occupied as unoccupied. Does the author mean to tell us that events exist physically but that times, though they exist, do not exist physically?

 

Connected with this lack of clarity is the following objection. Presentism is usually explained as the view that temporally present items (whether times or events or members of other categories) alone exist, and thus that wholly past items and wholly future items do not exist, where 'wholly' rules out overlap with the present.   If that is what is meant by presentism, then W. hasn't captured it in his definition.  For if present items are a proper subset of all existing items (spatiotemporal locations  and events at those locations) then those past and future items also exist. But then we are no longer talking about presentism.  Presentism is precisely the denial of the existence of the past and the future. The author appear to be begging the question in favor of eternalism by assuming that eternalism is true and that presentism can be defined in terms of it.  This ignores the fact that eternalism and presentism are mutually exclusive.

 

If presentism is the logical contradictory of eternalism, then what exists according to presentism cannot be a proper subset of what exists according to eternalism.  The author my be fudging the issue with his obscure talk of physical existence.

 

3) We were told that presentism partitions M into past, present, and future events.  Now what makes present events present? Here is where simultaneity comes into the picture.  Simultaneity is an equivalence relation (reflexive, symmetrical, transitive) that effects the partition that creates a proper subset of events, the present ones, and distinguishes them from those to their past and those to their future.  This puzzles me for a couple of reasons which I will sketch now, and try to explain more clearly tomorrow.

 

First, the present as we experience it is not punctuate but specious, in William James's sense of 'specious.' It has a certain spread or duration.  'Now' in 'The sun is now rising' picks out a short period of time that had not yet begun when the sun was below the horizon and will be over a short time later, say in an hour. Sunrise is not an instantaneous event by a a process.

 

Second, how does what the author says distinguish the present present from past and future presents? After all, at every time or temporal location t in M there is an equivalence class of simultaneous events at t. It follows that there are many -- continuum-many! -- presents, each equally present at itself.  The present present, however, is not merely present at itself, but present simpliciter. It is the 'privileged present,' the absolute present.  Presentism is committed to an absolute present. So again, it seems that our author has not put his finger on what privileges the present present, and distinguishes it from past and future presents.

 

Comments

[Malcolm Pollack]

Hi Bill, and thanks for continuing with this. A couple of thoughts:

I think physicists would push back on your distinction between spacetime points and spacetime events; my understanding is that the term "event" is simply a way of distinguishing the concept of a "point" -- which in classical usage identified a location in 3-D space -- from a location in the 4-D spacetime manifold. A quick search on Google and a query to Grok support this; here's Grok:

Spacetime points and spacetime events are essentially the same concept in the context of relativity and physics. Both terms refer to a specific location in spacetime, defined by a set of coordinates—typically three spatial coordinates (x, y, z) and one temporal coordinate (t).

A spacetime point or spacetime event represents a single, unique "moment" in the four-dimensional continuum of space and time. For example, an event like a particle existing at a specific position at a specific time is described as a spacetime event or point. The term "event" often emphasizes something happening at that point (e.g., a collision or emission of light), but mathematically, they are identical, as both are just coordinates in spacetime.

So, in short: Yes, they are the same, with the difference being more about context or emphasis in usage.

(Forgive me if this seems a pettifogging quibble, but I'm not entirely sure how much of your argument's load it is going to have to bear.)

Regarding your objection in 2), the way I understand W.'s meaning is to say "that which the presentist considers to be 'all that exists' is a proper subset of what the eternalist considers to be 'all that exists'." Both will agree that what the presentist considers to exist does in fact exist; it is simply that the eternalist thinks a great deal more (i.e., everything in M that isn't picked out by whatever concept of "the present" we can agree on) exists as well. I can't see how that begs the question, but I might not be understanding your objection clearly enough.

Your section 3) zeroes in on what I consider the hard part for the eternalist: what makes this "present" the present?

Also, you write: "the present as we experience it is not punctuate but specious". But why should "as we experience it" be relevant to the ontology of spacetime? (Note that this is different from the relativity of reference frames in SR, which can be considered as objectively distinct frames regardless as to the conscious experience of the observer.)

[Joe Odegaard]

If two events are separated in space, it will be impossible to say that they happened at the same time. This expands presentism into quite a fog.

More info here about one of Einstein's famous thought experiments:

https://en.wikipedia.org/wiki/Relativity_of_simultaneity

[BV]

Malcolm,

Very helpful comment. And I would not think to accuse you of quibbling and pettifoggery. None of that is going on here by either of us. I think you and Grok -- smart 'guy' eh? -- are right about how physicists use 'spacetime points' and 'spacetime events.' I would have to grant that MATHEMATICALLY they are one and the same. But then we are abstracting from actual events in the PHYSICAL universe such as two subatomic particles colliding or an electron's quantum jump from one orbital to another.

Intuitively, even if something is happening at every temporal location, there is a distinction between the location and what is happening there. If you say NO then our physicist pals are blurring an obvious distinction. If they say: we don't need to make that distinction for our purposes, I'll grant that, but then suggest that physics, with its idealizations and abstractions, as incredibly useful as it is for the prediction and control
of macrophenomena simply does not engage the questions that philosophers want to answer.

I think I'm a compatibilist when it comes to the relation of physics and philosophy. Two different 'magisteria' that can peacefully coexist, albeit with certain concessions by those on either side. Compare the conflict between Genesis literally interpreted and the theory of evolution. I don't believe that the human race descended from two original parents, Adam and Eve, or that God literally walked around in the Garden of Eden. But let's not pursue this comparison now -- it will lead us too far afield.

[BV]

Malcolm,

As for my second point, I do see what you are saying in defense of W. But think about it this way. W. uses set-theoretical jargon to define the difference between the eternalist and the presentist. Now if set S1 has members/elements and is a proper subset of set S2, then S2 must have members/elements -- otherwise it is the null set. (Not A null set but THE null set: the null set is provably unique from the ZF axioms.) So isn't W. presupposing the existence of the entire 4D-manifold M and all equally existent spacetime points/events in M?

Presentism and eternalism are logical contradictories: they cannot both be true and they cannot both be false. They are mutually exclusive. But S1 and S2 are not mutually exclusive: every member of S1 is a member of S2, but not vice versa.

So, at best, W's characterization of the difference between presentism and eternalism is unfair, and smacks of begging the question in favor of eternalism.

Be that as it may. The deeper question is whether STR or physics generally entails eternalism, which is a metaphysical doctrine. Arguably, science oversteps its legitimate authority when it pronounces upon metaphysical questions -- and vice versa.

[Bill V]

Malcolm sez: >>Also, you write: "the present as we experience it is not punctuate but specious". But why should "as we experience it" be relevant to the ontology of spacetime? (Note that this is different from the relativity of reference frames in SR, which can be considered as objectively distinct frames regardless as to the conscious experience of the observer.)<<

That's good! A reasonable objection. I sense that we may soon be discussing Eddington's two tables.

Well, how does physical science start? It starts with experience, with the deliverances of the five outer senses. Of course, over the centuries we have learned how to instrumentally extend these senses by the invention and use of telescopes, microscopes, etc. You will grant that empirical/experiential verification is essential to science. Experience is CONSCIOUS experience. (Your 'man' Grok is not conscious.) Consciousness is first and foremost intentionality. And so we are back to MIND. We experience a changing world. But to experience change, which requires time, we must experience time, and we do, which requires that the present be specious not punctuate. Experiencing change, we experience temporal passage. We can abstract from passage B-theoretically, but trhen are we move towards reality or awat=y from it?

To make this really clear would take more time than I can invest at the moment: wifey wants me to cook her breakfast.

You are right about the inertial reference frames, but it does raise the question as to what exactly these franes ARE, and if we poke into this we may discover that observers need to be brought in.

[Malcolm Pollack]

Bill,

So much here!

"Intuitively, even if something is happening at every temporal location, there is a distinction between the location and what is happening there. If you say NO then our physicist pals are blurring an obvious distinction. If they say: we don't need to make that distinction for our purposes, I'll grant that, but then suggest that physics, with its idealizations and abstractions, as incredibly useful as it is for the prediction and control of macrophenomena simply does not engage the questions that philosophers want to answer."

Is "what exists?" only a question for philosophers, or for physicists as well? (I realize that this question is itself a philosophical question.) A physicist will say that M exists, as do the points/events it contains. (Whether it is continuous or discrete is another question.)

"...at best, W's characterization of the difference between presentism and eternalism is unfair, and smacks of begging the question in favor of eternalism."

I'm not persuaded; all I think W. is saying that "if M exists, then the present is a proper subset of it"; this does not exclude the possibility that "M does not exist, and so the present is all there is." I think we can be charitable enough to say that he's not question-begging; he's just setting up the two sides of the debate.

"Well, how does physical science start? It starts with experience, with the deliverances of the five outer senses. Of course, over the centuries we have learned how to instrumentally extend these senses by the invention and use of telescopes, microscopes, etc. You will grant that empirical/experiential verification is essential to science."

Yes, physical science starts with the senses, but it doesn't end there; it makes claims about physical reality that purport to be quite independent of whether anybody's actually looking. (The most controversial and mysterious parts of modern physics are precisely those parts of quantum-mechanics where it's difficult to keep the observer out of the picture.) And much of the progress in modern fundamental physics came not from empirical observation, but from purely analytical results in mathematics, with empirical confirmation only provided much later, often with great difficulty.

The dispute here between presentism and eternalism is about ontology, about the bedrock of reality. Is that dependent on conscious experience? Is presentism/eternalism really a debate about idealism/realism?

To look at this another way: for the presentist, how "thick" is the present? At its limit, does the duration of the "present" set of simultaneous points/events become infinitesimal, in the sense of a 3-D geometric hypersurface dividing M into past and future, the way a geometric plane would divide a solid? (I'm leaving aside for the moment the problem of reference frames and simultaneity in SR.) Is such an infinitesimal "present" acceptable to the presentist? Or do presentists usually insist that the present has an ontological "thickness" that springs into existence entirely as a result of our subjective experience? (I don't know enough about the literature to answer this.)

If the ontology of presentism really does depend on our subjective experience, though, how does presentism account for the varying "speciousness" of "the present" that different conscious observers might experience? Does each of us create a personal "fact of the matter" about what exists and what doesn't?

I have to say, as I've mulled this over in writing this comment, that the case for eternalism is looking better and better -- at least if we want to hang on to some sort of objective realism (which, of course, maybe we don't).

[Bill V]

Malcolm,

I have been trying to find an online version of E. J. Lowe, "Presentism and Relativity: No Conflict." No success, so far. W. responds to Lowe, and it would be useful to compare the approaches of these two. This paper is published in the same volume in which W's paper appeared.

To help focus our discussion, I will advance some theses. You tell me whether you agree or disagree, and why.

1. Scollay Square (SS) no longer exists. What this means is that this square existed (past tense) but does not exist (present tense.) So far, no metaphysics: just the citation of an empirical fact using ordinary (as opposed to philosophical) English understandable by anyone competent in English.

2. (1) prompts some of us to ask philosophical questions which seem to make sense. One of them is whether SS, which is wholly past -- I trust you understand what I mean by 'wholly past'; if you don't I will explain -- is in any sense real or exists in a sense different from the sense of the present-tensed 'exists.'

3. And now four philosophical theories.

A. The question just posed does not make sense. It is a pseudo-question sired by a misuse of language. (Wittgenstein)

B. The question does make sense and the answer is extreme presentism: Of all that exists in time (as opposed to 'outside' of time) only what exists (present-tense) exists simpliciter. This implies that SS, when it became past, became nothing: it was annihilated by the passage of time. (E. J. Lowe)

C. The question does make sense and the answer is (so-called) eternalism: SS and all wholly past items (of whatever category) exist in the same sense and in the same way as all present items. (I do not mention the future, to keep the discussion simple and focused.) They all exist with equal robustness, to use a Russellian word.

D. The question does make sense and the answer is some form of mitigated presentism. The mitigated presentist does not hold with Lowe that the passage of time annihilates the present items. The mitigated presentist tries SOMEHOW (there is more than one way) to uphold the reality of the past. I won't now list the different ways. But here is one way: a mitigated presentist might say that the reality of a wholly past event is adequately accommodated by the causal traces of that past event in the present.

[Malcolm Pollack]

Hi Bill,

3a) I'm not familiar with Wittgenstein's argument for this position, and I don't know why the question doesn't make sense. (It seems like a reasonable enough question, but I'm not Wittgenstein!)

3b) This seems intuitively plausible (very much so!), and as I've said elsewhere in ths conversation, I can see various ways to describe how a continuously evolving bridge, passing through whatever exists in each present moment, can maintain a causal chain between past and present. But it seems at odds with relativistic physics in ways that are costly to resolve.

3c) This seems cleanest and most parsimonious, except for the enormous, gaping mystery of our experience of time - which is no small thing!

3d) I don't know enough to comment. (I suppose this is the "ersatzer" model, but I don't understand it well enough to have a worthwhile opinion.)

[Michael Brazier]

To the Aristotelian, time is the result of change, not vice versa; change does not assume the passing of time, but generates it. Because a change takes place within a substantial thing, or among such things, and things don't exist for one infinitesimal instant, change is specious, and therefore so is time. Any punctuate measure of time is assigned by an outside observer for purposes of calculation; it is not a real feature of the world.

[BV]

Malcolm,

Thanks for addressing my points head-on.

Your inclination towards eternalism puts you in very good company, and eternalism easily accommodates the reality of the past: it is just as real/existent as the present and the future! But consider the following.

Long ago, in ancient Rome's coliseum, gladiatorial battles took place. No one will say that such battles are still going on, or that any such battles are occurring at present. But if eternalism is true, and a past gladiatorial battle is as real/existent as a present battle in the Ukraine, say, except that the first occurs at an earlier temporal location than the latter, then it seems that the gladiatorial battles are tenselessly occurring -- which is highly counterintuitive.

Suppose time travel is possible. Suppose we travel back in time to the gladiatorial battles in the Coliseum. Will we find slaughter going on there? If so, then the name 'eternalism' will be most apt: the slaughter will continue eternally. But this is highly counterintuitive!

Hermann Minkowski famously said, "Henceforth space by itself and time by itself are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality."

And so some have protested that eternalism involves the illicit spatialization of time, and also I suppose, the temporalization of space, which yields spacetime points, thus stretching the term 'point' from its 3D use to a possibly illicit 4D use.

But of course this protest presupposes, contra Minkowski, that space and time cannot be blended into spacetime.

In sum, one objection to eternalism is that it illicitly spatializes time. There are others which I will mention later.

[BV]

Michael,

Time has both a static and a dynamic side. Time seems to pass or flow. This dynamism we call temporal passage. It corresponds to McTaggart's A-series; the static side corresponds to McTaggart's B-series: the series of events ordered by the B-relations (earlier than, later than, simultaneous with). Both sides need to be taken into account.

As for change (whether substantial/existential, accidental/alterational, mereological, or relational) it arguably presupposes the B-series. No change without time if a thing's alteration is its having different properties at different times.

[Malcolm Pollack]

Bill,

"Long ago, in ancient Rome's coliseum, gladiatorial battles took place. No one will say that such battles are still going on, or that any such battles are occurring at present. But if eternalism is true, and a past gladiatorial battle is as real/existent as a present battle in the Ukraine, say, except that the first occurs at an earlier temporal location than the latter, then it seems that the gladiatorial battles are tenselessly occurring -- which is highly counterintuitive.

Suppose time travel is possible. Suppose we travel back in time to the gladiatorial battles in the Coliseum. Will we find slaughter going on there? If so, then the name 'eternalism' will be most apt: the slaughter will continue eternally. But this is highly counterintuitive!"

Well, there's the problem for eternalism, as I've noted before: it offers no explanation for the subjective experience of time's passage; for why the fundamental fact of our experience is a succession of "nows" that come and go; for the sequential privileging of small (but not infinitesimal!) slices of M as "now". I think it must be connected deeply, or even somehow identical with, that other titanic mystery, namely that of consciousness.

But what's the answer? Hypotheses non fingo.

"And so some have protested that eternalism involves the illicit spatialization of time, and also I suppose, the temporalization of space, which yields spacetime points, thus stretching the term 'point' from its 3D use to a possibly illicit 4D use.

But of course this protest presupposes, contra Minkowski, that space and time cannot be blended into spacetime.

In sum, one objection to eternalism is that it illicitly spatializes time."

Nevertheless, time and space do indeed seem to blend as SR and GR predict: those who pass through space in different ways pass through time differently as well. A space traveler making a high-speed round trip to a nearby star (which, our classical intuition would say, is just a journey through space alone) comes home to find that he's aged less than the people he left behind. I don't think this is now controversial at all, at least among physicists.