Wednesday, October 14, 2020

Eternalism vs. Presentism

Eternalism is the view that the past, present, and future all exist. Presentism is the view that only the present exists. You may know these as the B theory and the A theory of time, or the static theory and the dynamic theory of time.

Eternalism = B theory = static theory

Presentism = A theory = dynamic theory

I've been undecided on these two views for a few years now. Before that, I came down pretty strongly on the A theory side. Before that I held inconsistent views.

I used to believe that God existed outside of time, and that the whole spectrum of time was laid out before him as if it were all "now" from his point of view. That's basically eternalism.

But at the same time I remember I used to say the present is all that exists. The past was gone, and the future hasn't arrived yet. I used to marvel at how our entire existence was an instantaneous moment that existed between the boudnary of the past and the future. That's basically presentism.

So yeah, I was inconsistent but didn't realize it until I started reading William Lane Craig. That was way back in 1999 or thereabouts. I have subscribed to the A theory of time most of the time since then. But I started to really have doubts a few years ago, and I've been undecided ever since, though I often lean one way or the other.

Why I think the B theory might be true

The major reason I think the B theory might be true is because of special relativity. According to relativity, there is no absolute simultaneity. Two events can happen one after the other from one person's frame of reference but be simultaneous from another person's frame of reference, and neither is wrong. This all follows from the fact that light travels at the same speed from the perspective of everybody in every frame of reference.

So imagine there's a train going by, and there's a lightbulb in the middle of one of the cars and a person on that car with the lightbulb. If the light bulb is exactly in the middle of the car, and if it turns on, light will reach each end of the car at the same time from the perspective of the person on the car. That's because in his frame of reference, the light bulb isn't moving. He and the lightbulb are stationary, and when the light comes on, light travels at the same speed in all directions, so it hits each end of the car at the same time.

But now think of it from the perspective of the person on the ground watching the car go by. From his perspective, the lightbulb is moving to the right, but when it comes on, light travels to the right at the same speed as it travels to the left. And since the car is moving to the right, the light will hit the left end of the car before it hits the right end of the car. That's because the left end of the car is moving toward the light, and the right end of the car is moving away from the light. So it hits the left end first.

So from the perspective of the person on the train, the light hits each end of the car simultaneously. But from the perspective of the person on the ground, light hits the left end of the car before it hits the right end of the car.

Think about that. Consider the moment at which the light hits the left end of the car for both observers. That means the moment at which the light hits the right end of the car is "the present" for the person on the train, but it's "the future" for the person on the ground. I can't see any way to understand this except to say that the present and the future both exist, which suggests a B theory of time.

Why I think the A theory might be true

The A theory of time appeals to me primarily because that is the common sense way to see the world. It conforms most accurately to our every day experience of the world. We only exist in the present, and the present is moving in the future direction. The past is over, and the future lies ahead.

There also seem to be problems with the B theory. On the B theory, there doesn't seem to be any exlpanation for why time has a direction. Sean Carroll thinks the direction of time is explained by entropy. But I don't see how that explains anything at all. Granted, entropy increases in the future direction, but how does that amount to entropy defining or causing the direction to be in the future? Assigning a direction to time on a B theory seems arbitrary. In fact, on a B theory, I see no reason for entropy to increase or decrease in either direction. The fact that it only increases in one direction seems arbitrary.

On the B theory, you'd have to dismiss the flow of time as an illusion. As I've explained in another post, I think if you have to dismiss some of your evidence as illusion, that is as much as to say that your model doesn't account for all the evidence. But besides that, the B theory doesn't even explain why the illusion exists. Why does it even seem like time is moving forward?

If the flow of time is an illusion, then it seems like backward time travel would just be a matter of psychology. One could theoretically travel backward or forward in time through meditation or some other psychological manipulation. After all, we would be four-dimentional beings who have extention both in space and in time. Our minds consist of the whole thing, not just one moment. So there's no reason why the mind couldn't subjectively experience any of the moments in any order. But we seem to only experience one moment at a time in one direction (language is failing me here).

Backward time travel also seems at least theoretically possible on a B theory of time without being a mere matter of psychology. You couldn't travel to an early moment of time if there was no early moment of time, but on a B theory there is. And since both space and time can be bent and warped, it's theoretically possible to bend it in such a way as to create a loop allowing you to go back to the past. But backward time travel leads to all kinds of paradoxes that are impossible. If the B theory leads to impossible paradoxes, and impossible paradoxes cannot be real since they are impossible, that seems to cast doubt on the B theory.

Causation seems to make better sense on an A theory than on a B theory. On the A theory, one thing really does cause another thing. But on a B theory, everything just kind of sits there. I don't see how there can be causation. On an A theory, there's a finality to the past, but the future can be caused to be one way or another. On a B theory, the future is just as final as the past, which is counter-intuitive.

Indeterministic interpretations of quantum physics make more sense on an A theory than a B theory. On a B theory, everything that happens is fixed and definite, but according to indeterministic interpretations of quantum physics, that isn't the case. There are probabilities attached to events, and things could go in a multitude of different ways. This isn't my strongest reason for thinking the A theory is true since I'm also undecided on interpretations of quantum physics.

Some other considerations

William Lane Craig doesn't deny relativity, but he thinks it's only apparent. He says that clocks slow down and speed up depending on their frame of reference, but that doesn't mean time itself slows down and speeds up. He thinks there is absolute time and absolute simultaneity, and that this doesn't conflict with our observations. He makes a disinction between our observations concerning relativity and our interpretation of those observations. He doesn't thiink it's necessarily to interpret the observations the way they are commonly interpreted. He didn't just make all this up either. He cites Hendrik Lorentz for his interpretation of relativity. I am skeptical of his view, but I don't completely understand it either. He talks about it with Roger Penrose in this discussion of Unbelievable from 56:10 to 59:20. The possibility of him being right does make the A theory a viable option for me.

Apparently, not all physicists agree with the static view of the universe either. Some of them think it's a convenient model, but that it doesn't map on to realty. Brian Greene has some videos on YouTube where he explains space-time like a loaf of bread where "now" slices can be sliced at different angles so that one person's present can be another person's past. He definitely subscribes to the B theory. But Nick Lucid is a presentist. I asked Nick about that one time, and he said he thinks physicists present the B theory to popular audiences because "it bewilders people and that's good for TV," not because they necessarily think that's how reality is. I'm not sure what Nick's education is, but he did author a book called Advanced Theoretical Physics, so I assume he's a legitimate physicist.

In another post, I explained how I think we ought to affirm the obvious rather than deny the obvious. We should think things are just like they appear unless we have good reason to think they are not. The A theory seems, prima facie, to be the correct view. It's the most obvious one. But this may be one of those situations in which we have good reason to think reality is very different than it appears to be. The argument from relativity I mentioned above seems solid to me. I acknowledge the possibility that it's wrong just because there are people smarter than me who disagree with it, but again the "seemingness" of the soundness of the argument makes me lean in favour of that interpretation. But on the other hand, the intuition about the A theory of time is very strong, and I'm not sure if the argument for the B theory is strong enough to overcome it. It's similar to how Zeno's paradoxes appear, at first glance, to be strong arguments against the possiblity of motion, but our intuition that motion is real is more than adequate to convince most people that there's a solution to Zeno's paradoxes even if they don't know what that solution is. So mahybe there's a solution to the argument for the B theory, and I'm justified in believing in the A theory even if I dont know how to refute the argument for the B theory.

These are all my thoughts, and the bottom line is that I am currently undecided.

8 comments:

Psiomniac said...

I think it's interesting to think about whether a global skeptic is susceptible to those criticisms in a way that they ought to care about. Supposing I come to you and say, I'm really confused because I can't see how I can know anything, like even if there is an external reality. You can say I can't rationally assert that I can't know anything, but I reply 'you might know that, I don't. Besides, I don't assert that I know I don't know, I just don't see at the moment how I could know and you don't seem to be able to fix that either.

It is like if somebody is confused, you might argue with them that on rational grounds they ought not to be. But from their perspective, you might not be able to offer anything that dispels their confusion. So how can you rule out the notion that they might be justifiably confused?

Sam Harper said...

I think the only way to be a consistent global skeptic is to not say anything at all. Because anything they say carries with it the assumption that it's an item of knowledge. They have some reason/justification for saying it even if they can't put their finger on what that reason/justification is.

Usually in my experience with people who claim they don't know anything or that they know very little, they are using "knowledge" in a peculiar way. For them, "knowledge" is roughly the same thing as "certainty," which is not how I use it or how I think most people use it. But if we take knowledge to be "justified true belief," and if somebody say something, then presumably they believe it, and they think they have some justification for believing it. If they believe it, then they must think it's true since that's what it means to believe it. So by the "justified true belief" definition of knowledge, by saying anything at all, a global skeptic is implicitly making a claim to knowledge.

If a global skeptic wants to avoid self-contradiction by saying, "I don't assert that I know I don't know," then they are essentially admitting that maybe they do know something. And I think that in reality, they do know some things even if they are unaware of it. At the very least, they know the content of their own minds, which is what enables them to give these autobiographical details about themselves, e.g. that "I am really confused," and "I don't know that," and "I don't see how I could know that." These are all claims the skeptic is making about himself that presumably he knows to be true.

Psiomniac said...

That's the point I am making though, that a global skeptic can say anything they like to express their confusion without a commitment to knowing that they don't know anything. Even what you take to be statements of implicit knowledge, like 'I am really confused' would only be contradictory if taken as an (implicit) assertion of knowledge that there is an 'I' doing the thinking. As the extensive criticisms of the Cogito point out, this is to beg the question, it posits an 'I' and assumes that it is doing the thinking. The skeptic might respond 'I know I said 'I', but I lack a form of expression that tracks my confusion. Or at least, it feels that way, I'm confused!'

Sam Harper said...

I would agree they are confused! My point is that one cannot be a consistent global skeptic while making claims about themselves or anything else. Their inability to figure out how to express their own confusion without using the first person personal pronoun is just evidence of the inconsistency inherent in global skepticism.

Psiomniac said...

I'm not sure that would bite the skeptic. Why would a global skeptic sign up for the norm of consistency? Might they not also point out that your own position is also inconsistent? as a fallibilist particularist you believe a set of propositions, say P1, P2,... Pn. You also believe that it is highly probable that at least one of them is false (or you ought to). Let's call that Pn+1. Then P1, P2,... Pn+1 forms an inconsistent set.

Meanwhile I realise I have posted this in the wrong thread, sorry! I have long followed the A-theory and B-theory arguments, so I might say something about that next.

Psiomniac said...

On the time's arrow explanation from the second law, it isn't arbitrary as I understand it. We remember the past but not the future because the act of remembering increases entropy. At least, I heard that explanation once, and with detail it seemed plausible, but I can't track it down!

I think on the general point of common sense realism, if a model predicts observations and is incompatible with common sense, so much the worse for common sense.

Sam Harper said...

>Why would a global skeptic sign up for the norm of consistency?

That is a good point. I guess if they were consistent, they wouldn't. Ha!

>Meanwhile I realise I have posted this in the wrong thread, sorry!

No worries. I didn't notice it right away either.

>We remember the past but not the future because the act of remembering increases entropy.

I'm sure there's something to Sean Carroll's argument that I just don't understand, but this doesn't really explain anything to me. It seems like any thinking, whether remembering the past or predicting the future, would increase entropy.

>I think on the general point of common sense realism, if a model predicts observations and is incompatible with common sense, so much the worse for common sense.

Except that without "common sense," you'd never be able to draw conclusions from observations in the first place. I addressed this in another post.

Psiomniac said...

>I'm sure there's something to Sean Carroll's argument that I just don't understand, but this doesn't really explain anything to me. It seems like any thinking, whether remembering the past or predicting the future, would increase entropy.<

Yes, but remembering is fundamental to all thinking, you couldn't predict anything if you weren't able to remember anything upon which to base your prediction. So if time's arrow align with low -> high entropy, and that's also the only way our experience can work, that makes sense?

>Except that without "common sense," you'd never be able to draw conclusions from observations in the first place.<

I'm not advocating abandoning common sense as a useful heuristic. Ideally, when observations are incompatible with common sense, the model should be extended to explain why that is so though. For example, if a convincing explanation of why thought can only proceed in the direction of low -> high entropy in a B-theory context did emerge, it would account for why we experience time passing. So that would account for our experience rather than dismissing it.