Recap: Alyssa Ney's Metaphysics: Chapter 8 - Time (Part 2)

Part 1: Time and methodology

So Ney presents us with four ‘metaphysics of time’:

1) Presentism

2) Growing block theory

3) Moving spotlight theory

4) Eternal block theory

These theories answer just two questions about time: The dynamic / static question and the ontology question. Is the passage of time real (dynamic) or illusory and relative to an observer (static)? Do objects and events cease to exist as they go into the past, and come into being as they become present, with only the present moment being real (Presentism)? In other words, is ‘temporal becoming’ a real feature of the universe, or only a feature of our minds (Eternalism)? Are there absolute tensed facts, or can all tensed facts be relativized into tenseless terms?

There are many other questions about time that I have. What is time itself? Does change give rise to time, or does time give rise to change? Is time separable from space, or are we always talking about one thing, spacetime, when discussing either space or time? Is time and/or space discrete or continuous?

I also have methodological questions. What does a naturalized metaphysical philosophy look like with respect to time? In other words, if we defer to physics and physicists on questions of time, how does that shape the philosophical debate around time? If time is the subject of an empirical science like physics, then should philosophers simply remain silent on time and let the physicists talk?

I have a friend who is a PhD student in physics, and here is his idea of what time is. Paraphrasing him, time is a vague notion that must be operationalized to be useful and meaningful. He gives the analogy of intelligence. If you wish to measure intelligence, then you have to get specific about what it is you are measuring, and then ‘intelligence’ will refer to that measurement. So if you design tests to measure someone’s ability to recognize patterns, then ‘intelligence’ will refer to ‘the ability to recognize patterns’ or ‘the ability to do well on pattern-recognition tests.’

Time is operationalized by clocks. A clock is a counter that counts time using ‘ticks.’ Basically, we swing pendulums and count the pendulum swings, and that’s all time is, a number of pendulum swings, or, the number on a clock. It’s up to us to measure time in ways useful to us. The problem with clocks is that there are discrepancies at very precise levels. Each ‘tick’ does not necessarily have the same duration, resulting in the need for leap seconds to sync things back up. One clock is the rotation of the Earth on its axis. A day is defined as one full rotation. But Earth’s rotation slightly changes over time. This is why atomic clocks are now used, as they have the most consistent ‘ticks’ over time. But there are many clocks that scientists use, and we can compare them all to each other to have a general idea of what time it is, and basically if a majority of our best clocks give us one time, then we use that as the ‘real’ time and synch up other, less reliable clocks to that. So if we want to know how many days it has been, defined as full rotations of the Earth, the problem is that one day doesn’t last the exact same amount of time as another day. So to make the days ‘even’ in their ticks, that’s when leap seconds are added. We do this on a bigger scale too, with leap years adding February 29th to our calendar to compensate for discrepancies in our calendar measurement. 

When I mentioned things like Presentism vs Eternalism, and A-Theory vs B-Theory, he said physicists do not talk about these things. So that makes me wonder, should we just toss out these debates if physics is not concerned with them? If time is an empirical matter, and these philosophical debates cannot be empirically settled, then does that mean philosophers are barking up the wrong tree? Or are philosophers asking good questions about time, and time isn’t a fully empirical topic?

And as someone who plays around with bundle theory as a theory of objects, I wonder how bundle theory is meant to handle the question of time. I think of bundle theory as something of a methodology in its own right. When asking any “What is this thing?” or “Does this exist?” kind of question, bundle theory wants to say, “Well, what properties can we not dispense of? Then those properties exist. Or really, then those properties are ones we cannot dispense of.”

Temporal properties are certainly ones we can’t dispense of. Some bundles of properties certainly exist in before-than and after-than relationships to other bundles. The Eiffel Tower was constructed after the American Civil War ended, and before WW1 began. So ‘before’ and ‘after’ are real properties that are relational properties, just like spatial properties.

We can dispense of the properties of past objects and future objects, as we don’t “bump into” those, so bundle theory would take a Presentist approach to time.

With all of that said, before we get into debates on these views, how popular are these competing views among philosophers?

Part 2: Sociology of views on time

The moving spotlight view is not even mentioned in these polls. Ney mentions that it’s not a popular view. Eternalism + B-Theory, which is the block universe view, is in the lead with about 40% in favor.

Because ‘Presentism’ can refer to both an ontology of time and a metaphysics of time, and because the moving spotlight view is not very relevant, I will take the liberty of using ‘Eternalism’ instead of ‘block universe theory.’ Ney discusses only arguments for and against Presentism and Eternalism as they are the most relevant views.

I won’t discuss growing block or moving spotlight. If you want to look further into those, be my guest. The SEP article on time discusses the growing block and moving spotlight theories: https://plato.stanford.edu/entries/time/. Curiously, the SEP article makes it a point to say that growing block is not committed to four-dimensionalism, but Ney describes growing block as four-dimensional page 222.

I’m skipping over these discussions both for the sake of time and space (no pun intended) and because I’m worried enough already that the Presentism vs Eternalism debate is a bad approach to time, because these debates are about something that should be empirically tested (time and space) and yet the presentism vs eternalism debate does not seem to interest physicists. So if it’s not clear what the use is in discussing Presentism vs Eternalism, despite those being the two most important views on time in philosophy of time, then it’s all the more unclear the use in discussing less relevant views (at least, until methodological worries have been assuaged).

Part 3: The argument from special relativity

There are two key arguments in favor of eternalism: special relativity and truthmaker theory. We’ll begin with special relativity.

Special relativity is Einstein’s theory, which has two key postulates:

1) The laws of physics are the same in all inertial reference frames.

2) The speed of light is the same for all observers.

Inertial reference frames are systems without acceleration, where all objects involved have steady velocity. To understand the first postulate, Ney has us imagine two people. One is sitting on a bench, and another is running by. The first postulate is simply the idea that physics applies to both people in the same way despite differences in velocity.

To understand the second postulate, Ney introduces a third person, another runner, who is running in the opposite direction of the first runner. Both runners are running 10 km/h. Relative to the stationary person, runner 1 has a velocity of 10 km/h. But relative to runner 1, runner 2 has a velocity of 20 km/h.

(You may have heard that two cars going 70 mph and crashing into each other is equal, in terms of relative speed, to one car going 140 mph and crashing into a stationary car. This is the same idea.)

We can apply this idea to demonstrate the “relativity of simultaneity.”

Ney has us imagine Einstein’s thought experiment of someone standing in front of a moving train. This stationary person sees two lightning strikes occur at the same time, one behind the train and one in front of the train. While the lightning strikes are simultaneous for the stationary man, they are not simultaneous to the man on the train, who sees the front lightning strike first and then the back lightning strike a bit later, because the light from the back strike has to catch up to the train.

So relative to the stationary man, the lightning strikes are simultaneous, but relative to the man on the train, the lightning strike in front of the train happens before the strike behind the train. (We can imagine a second, faster train, where a man on that train sees the front lightning strike occurring even sooner and back strike as occurring even later, for a greater total discrepancy, compared to the experience of the man on the first train.)

But if presentism says there is a real, objective present moment, but special relativity says simultaneity is relative and not absolute, then it looks like special relativity counts against presentism.

According to Minkowski spacetime, the following is true:

• There aren’t 3D objects persisting through time, but rather time is like another spatial dimension, resulting in a 4D spacetime block. This is called Minkowski spacetime.
• So we have a fourth axis, t, that allows one to specify the spatiotemporal location of an object on an x,y,z,t coordinate system.
• There is no preferred or objective partition of this spacetime manifold into slices of spacetime. Different observers moving at different velocities will have different spatiotemporal experiences. In other words, what’s true about space and time is true with respect to subjects, and so you can have contradictory, and yet equally true, spatiotemporal experiences.
• There are objective facts about distances between spacetime points, but no objective fact about space or time itself, i.e., spatial distances or temporal durations.

Ney mentions, to my surprise, that the main move for defenders of presentism is simply to deny special relativity, or at least deny Einstein’s interpretation of it. Ney references a few defenders of presentism in light of special relativity. These include:

Mark Hinchcliff: “A Defense of Presentism in a Relativistic Setting”

William Lane Craig: Time and the Metaphysics of Relativity

You can get some ideas of Craig’s view from his website reasonablefaith.org, such as in this QnA: https://www.reasonablefaith.org/writings/question-answer/how-do-i-interpret-general-relativity-theory

For something more scholarly, see: https://www.reasonablefaith.org/writings/scholarly-writings/divine-eternity/bergson-was-right-about-relativity-well-partly 

And Ned Markosian: “A Defense of Presentism.”

More generally, Dean Zimmerman has defended presentism in Contemporary Debates in Metaphysics, edited by Theodore Sider, John Hawthorne, and Dean Zimmerman.

Theodore Sider defends eternalism, and so does Hilary Putnam, DC Williams, and JJC Smart. (I don’t have citations for this but Alex Pruss and Kenny Pearce also defend eternalism.)

Ney mention’s Simon Keller’s “Presentism and Truthmaking” as a good resource for discussion on the objection to presentism from truthmaking, which I will turn to next.

Part 4: The argument from truthmaker theory

When something is true, in virtue of what is it true? What makes something true? Why are true things true? What do we mean when we say a certain claim is true?

If we can’t answer these questions, then we run the risk of rendering truth meaningless. If someone makes a truth claim, say, that “Philosophy is a waste of time,” and I ask “What does that mean?”, and they respond with “I don’t know,” then I cannot agree with what the person said because what the person has said is admittedly meaningless.

More generally, it’s hard to get excited about truth claims, or truth in general, if we don’t know what they are or what they have to do with us.

I say this because some philosophers want to make truth out to be some kind of basic, primitive, unanalyzable notion (Graham Oppy is an example). But this approach lacks explanatory power in an area, truth, that desperately needs explanation, because as noted above, if we cannot explain what it means for something to be true, then I don’t see why I can’t just dismiss all truth claims as meaningless. (Or, I could dismiss all truth claims that I don’t like as meaningless and accept the ones I do like as meaningful. You could claim this is cherry picking or being inconsistent, but what would it mean to claim such a thing? Would it in fact be true that such an approach would be inconsistent? In virtue of what? And why would inconsistency be bad? In virtue of what would it be true that inconsistency is bad?)

So if we want truth claims to be meaningful, then something has to ground them. These are truthmakers. Truths are true in virtue of their truthmakers, whatever ‘truthmakers’ happen to be. This leads to a certain principle called truthmaker maximalism. 

Truthmaker maximalism = The view that all truths have truthmakers. There are no truths that are brute facts.

Truth clearly has something to do with reality. So the most obvious candidate for a truthmaker, for that which makes a truth true, is reality. If a claim corresponds to reality, then it’s true, and if it fails to correspond, then it’s false.

Usually, we say facts are truthmakers, with facts being particular states of reality. So the claim “The Eiffel Tower is 330 meters tall” is made true by the fact that the Eiffel Tower is 330 meters tall. The claim “The sun revolves around the Earth” is made false by the lack of the corresponding fact.

Now the argument against presentism (241):

1) All truths have truthmakers.

2) If all truths have truthmakers and any sentence about the past and future are true, then their truth will require the existence of past and future objects or events.

3) Some sentences about the past and future are true.

4) So, there must exist some past and future objects or events.

5) If presentism is true, no past or future objects or events exist.

6) Therefore, presentism is not true.

Presentists cannot reject 4 and 6, as those are conclusions that logically follow. They cannot reject 5, as that’s just part of the definition of presentism. So they must reject 1, 2, or 3, or some combination thereof.

Ney shares two ways the presentist might try to deny 1. First, they might just deny truthmaker maximalism and allow for ungrounded truths. I think this is a terrible option for reasons noted above. Here you might give the “funny facts” objection against truthmaker maximalism. Consider:

Unicorns do not exist.

What fact grounds this statement? Above I mentioned a claim being false in virtue of a lack of a corresponding fact. But someone might think a lack of a fact cannot ground a truth, as only positive things can act as grounds. But I do not (yet) see the issue in letting falsehood just mean a lack of a corresponding fact. “There is at least one unicorn” is false; there is no unicorn to make it true. So “unicorns do not exist” is true. So I do not see funny facts to be a problem.

Second, a presentist might deny 1 by accepting “temporal fictionalism,” where they accept the past and future as a kind of fiction, and some truths can be fictionally true. The statement “Harry Potter is a wizard” is fictionally true, that is, true with respect to a fictional story. Likewise, claims about the past or future can be true with respect to a fictional story.

I don’t like this either. Saying “There were dinosaurs” or “Abraham Lincoln freed the slaves” is meant to say something more true than something like “Harry Potter is a wizard.” It seems to me the presentist would be better off to say that because temporal becoming is real, there was a time when “There are dinosaurs on the Earth” would have been made true by the real existence of dinosaurs. When the dinosaurs were wiped out, the sentence became false, but this sentence has a history of being made true. So when we say “Dinosaurs were on the Earth,” we are saying “‘Dinosaurs are on the Earth’ is a claim with a certain history such that it was once made true and then through temporal becoming was made false as things changed.” In comparison, “Harry Potter is a wizard” has no such history; this claim has never been made true by anything real.

The presentist could deny 2 on the basis of determinism. If determinism is true, then the past plus the laws of nature necessitate the future. So you wouldn’t need the future to be real to know what will happen. Claims of the future would be perfectly true, grounded in present facts about the laws of nature plus the current state of the world.

A potential problem with this move is that the laws of nature might not be fully known or understood until the future has unfolded a bit more. Or we could say that only an omniscient being, with full knowledge of the present state plus the laws of nature, could actually know whether a future claim is true. When we make future claims we have no reason to believe that it’s really the case that the present state of the universe plus the laws of nature actually ground that claim. So this would allow future claims to be grounded in the present, but we would have no way of knowing this to be the case for any given future claim we make until the claim is vindicated by the future becoming present.

The presentist could deny 3 and say that all claims about the past and future are false. But this sounds crazy, mostly because it’s obvious that past claims like “Dinosaurs once roamed the Earth” or “Washington owned slaves” are obviously true.

One way the presentist could fix this is by the following: accept the truth of past statements through the story I told above about the history of the truth of claims, but then deny the strict truth of future claims, interpreting future claims to really be claims about the present. On this view, past claims can be true, made true by the history of the present equivalent of the claim, but future claims are false.

“I will go to your party” really just means “There is a current intention in my mind to go to your party,” and “The Olympics will take place in 2028” really means “There currently are plans in place to have the Olympics in 2028.” The present equivalent of these future claims can be true, but strictly speaking the future claims are false.

(Dr. Patrick Todd argues that future contingents are false. See: https://www.youtube.com/watch?v=HmrOIqCEvQM)

Part 5: A few arguments in favor of presentism

Briefly, here are three arguments in favor of presentism.

The first argument is from intuition, experience, or epistemic access. I’ve heard phenomenal time referred to as manifest time. We experience the passage of time in a very direct way, such that it feels like the past is really gone and the future is not yet here. While eternalists call this experience an illusion, it may be that phenomenal time is matching up with reality as it is, and reality having certain features is what explains phenomenal time. As the universe expands, it takes time for objects to persist and undergo change, and those who have conscious experience will therefore always be, at the moment of their conscious awareness, at the “frontline” of the universe’s unfolding. This picture of things can feel right to some people, so much so that they struggle to imagine things being otherwise.

The second argument is from change. This was McTaggart’s argument against eternalism. On eternalism, it sounds like nothing changes, as there is a frozen snapshot of the history of time. For McTaggart, time needs change, and change needs a real past, present, and future.

Ney calls this a “legitimate concern about the B-Theory.” (236) A response from the eternalist, Ney suggests, could consist in making a distinction between the change of events and the change of objects. On eternalism, events are all set in stone in spacetime, but that doesn’t mean all objects are. More specifically, events don’t change their properties, but objects do.

I’m not sure what ‘event’ is meant to mean here. Is an event just a moment of change, of one object gaining or losing a property? I’m also not sure how McTaggart’s concern makes sense, and I’m not sure how Ney’s suggestion is meant to fix it. It seems to me that there is no problem of change on eternalism. Change is what explains why the 4D block looks the way it does. Without change, there is no time and no 4D block. But I don’t see why an objective present is needed for change.

Maybe there is a concern of how did the change occur unless the change really took place, and without real temporal becoming the change never really objectively takes place? Put another way: If the future is tenselessly there, then how did the future “get there” if the present needed to “happen” first? But if the present needn’t happen first, then why does there need to be this connection between the future and the present in the form of change? Why couldn’t the past, present, and future be disconnected if they are all real at once?

A third argument, hinted at on pg 237, is from consciousness. If I am to be identified with my conscious self, then clearly I exist now and I do not exist in the past or future. Sure, my past self was me, but we’re talking about how on eternalism there are apparently past, present, and future versions of me all existing simultaneously. But I have no conscious experience of existing in some past or future time, only now. And yet, if those past and future versions were really me, then they would share my properties. But of course, they do not share my properties, as I am conscious here and now and they are not. (And, they are conscious then and there and I am not.) So tenseless versions of me must be me, but they cannot be me. So, eternalism doesn’t make any sense. Or, eternalism implies there are countless conscious clones of me spread across my timeline, one clone per moment that passes, all stuck in their own moment. But as long as it feels like I don’t exist in the past or future, then it makes intuitive sense that nothing else would either.

Conclusion / Summary

• There are two main competing views in philosophy of time: Presentism vs Eternalism.
• Technically, we have two competing views here on the passage of time: A-Theory vs B-Theory.
• And we have two competing views on the ontology of time: Presentism vs Eternalism.
• Confusingly, philosophers combine A-Theory with Presentism to arrive at a view called Presentism, and they combine B-Theory with eternalism to arrive at a view called block universe theory.
• For simplicity, we can just call these two views presentism and eternalism.
• There are two main arguments in favor of eternalism: the argument from special relativity and the argument from truthmaker theory.
• Special relativity implies the relativity of simultaneity, which in turn implies there is no objective present, and ‘now’ is indexical and subjective just like ‘here’.
• Special relativity paints a picture of four-dimensional spacetime where time is treated like a spatial dimension, much in line with the block universe theory.
• Defenders of presentism often simply reject special relativity, or at least reject the interpretation of it that implies relativity of simultaneity.
• Truthmaker theory says that all true claims, to be meaningfully true, must be true in virtue of the way things really are. Facts, or states of reality, are what ground the truth of true claims, and the lack of a corresponding fact is what grounds the falsity of false claims.
• We take it to be the case that there are truths about the past and the future. And yet, if the past and future do not exist, as on presentism, then there is nothing in the past or the future to ground the truth of these claims.
• Presentists can deny (1) truthmaker theory, or deny (2) that the past and future must be real to ground past and future claims, or deny (3) that there are true claims about the past and future.
• I think denying truthmaker theory is a non-option.
• I suggest for presentists to deny (2) with respect to claims about the past. A true past claim like “Abraham Lincoln freed the slaves” is made true by the fact that temporal becoming is real, and so the truth of a claim like “Abraham Lincolm is freeing the slaves” is made true by present facts, and then made false as those facts change. Past claims are claims about a certain history of a claim’s being made true at one time. If temporal becoming is real, then claims take on a real history of being true at one time and then false at another (and false at one time and then true at another). And so claims about the past (and maybe even the future if a similar move can be made with respect to future claims) can be made true by that history. While presentists are committed to past objects / events being no longer real, they are not committed to the idea that past objects / events were never real. But if past objects / events were once real, then we have real history on presentism. 
• I suggest for presentists to deny (3) with respect to future claims, and instead interpret future claims as really being claims about the present.
• I feel agnostic about presentism vs eternalism.
• I worry about methodological concerns about the role of philosophy in discussing empirical issues like time. I wonder whether philosophers should just defer to physicists on this issue, or whether philosophers are asking substantial, non-empirical questions related to time.
• Physicists are not concerned about presentism vs eternalism and take time to be nothing more than whatever it is we measure it to be using clocks.