Tim Maudlin's Interesting View of Time Part 1October 27, 2017 Time: 21:45
The renowned philosopher takes a more traditional view of time.
KEVIN HARRIS: Come on in! Welcome to the Reasonable Faith Podcast with Dr. William Lane Craig. It's Kevin Harris. As we get into this podcast today I want to remind you we have new features on our website. Go to ReasonableFaith.org. Bookmark it. Go there often and see some of the new things that are going on right now at ReasonableFaith.org.
Today we're going to start a two-part series. It's an interview with philosopher Tim Maudlin on time. I am learning a lot from Dr. Craig just going over this interview with this renowned philosopher Tim Maudlin. Today, part 1 on Reasonable Faith.
We've talked about Tim Maudlin, a great philosopher, on several of our podcasts. We found this article of his, and it's an interview. I haven't read his book but he's talking about one of your favorite topics that you've written on – the reality of time. This is an interesting interview by Edwin Tse for Quanta Magazine. A couple of things about it. First of all, it seems to confirm a lot of what you've written about. It's also funny that in the introduction here he calls this view of time, this more traditional A-theory of time, “homey” and old-fashioned as if the newer theories of time that are out there are more exotic. But what do you think? Maudlin seems to be kind of rejecting some of those and saying no.
DR. CRAIG: As I read the interview it really does seem that Maudlin is endorsing the so-called tensed theory of time. That is to say that time is not like a spatial line that is stretched out before you but that time is characterized by a kind of temporal becoming. Now, there are aspects of the interview that suggests the opposite, I have to say. With all due respect, I'm not sure that Maudlin is entirely conceptually clear on these different views of time. Sometimes, as I read the interview, I get the impression that he does affirm what he calls (and many have called) a sort of block view of space-time – that all events in space and time are equally real and the whole four-dimensional block just exists tenselessly, and what he is adding is an intrinsic direction to time. One of these directions in space-time has an intrinsic directionality to it. That is entirely consistent with a B-theory of time. You could have a spatial direction even that has an intrinsic direction to it. Adding a direction to one of these dimensions doesn't turn it into time. But then, on the other hand, there are other places in this interview where he seems to explicitly affirm the notion of the passage of time and that things come into being. I think almost in spite of himself he does seem to be endorsing this tensed theory of time (or A-theory of time that you mentioned) and that lies at the foundations of the kalam cosmological argument as I have enunciated it. Because if a tensed theory of time is true, that means that the beginning of the universe represents the point at which the universe comes into being. It is not just a sort of tenselessly existing front edge. Rather the universe comes into existence out of nothing, that is to say not out of anything, and that surely calls for some sort of transcendent cause. So I think there are deep metaphysical or theological implications of this view of time. It seems to me that you're quite right that Maudlin seems very sympathetic to this view.
KEVIN HARRIS: In the first paragraph Edwin says, “Tim Maudlin thinks our direct impressions of the world are a better guide to reality than we have been led to believe.” I think what that is making reference to is this arrow of time – that time seems to have this forward motion.
DR. CRAIG: Yes, and our experience of time. I love what the interviewer says in this first paragraph. He says, “Physicists and philosophers seem to like nothing more than telling us that everything we thought about the world is wrong. They take a peculiar pleasure in exposing common sense as nonsense.” Maudlin challenges that and takes a stand with the common-sense man. And I say amen to that! I think it is absolutely true that our experience of time – our experience of tense and becoming – is fundamental and foundational, and any theory of reality that denies that is for that reason in real trouble.
KEVIN HARRIS: Maudlin is a philosopher of physics.
DR. CRAIG: Right.
KEVIN HARRIS: So time would be kind of a side-study of his.
DR. CRAIG: Except, you see, in the 20th century philosophy of time for a great many theorists became part of science because it was time as is studied in physics that became the object of philosophical speculation. That's very different from the way time has normally been understood. But one of the vestiges of positivism was what W. V. O. Quine called the abandonment of first philosophy. Rather it is science – physical science – that gives philosophy its marching orders, and so for many philosophers of time what they're studying is that entity in physics that goes under the name “time.” One of the fundamental challenges that I have issued in my work on time to this view is that what physics studies isn't really time at all. It's our measurements of time. It's our empirical measures of time that physics studies – clocks and things of that sort. But not time itself, which is a metaphysical reality that can exist wholly in the absence of any physical measures or even physical objects.
KEVIN HARRIS: Going down about the middle of the page – and there's a lot to this interview. We're going to try to get the high points here. He says, “Modern physics, he argues, conceptualizes time in essentially the same way as space. Space, as we commonly understand it, has no innate direction — it is isotropic.” What? Equally in all directions?
DR. CRAIG: Yes. It is the same in all directions. So there isn't any real up or down, so to speak, in outer space. Right? That is just your perspective of your observer. There isn't any literal objective here or there. In space everything is equal. There is no intrinsic direction to space. That isn't inherent to space itself. In Aristotelian physics, for example, space did have a direction. Aristotle thought the Earth was at the center of the universe and things have a natural tendency to fall downwards and to go toward the center – the sort of sinkhole of the universe where we were. Having a direction, as I said earlier, isn't sufficient to turn a spatial direction into a temporal direction. Some of the things that Maudlin says seems to suggest that it would. What differentiates time from space is that time does have a direction. In that sense it is different from space. Well, I think that's certainly true that whereas spatial dimensions don't have direction or an arrow, time does. It runs from past to future. But I see that arrow of time as rooted in a deeper metaphysical reality, namely the reality of temporal becoming – of things coming to be and passing away. That is why time has this arrow. But it's not sufficient to simply say that time and space are distinct because time has a direction. The question will be: why does it have a direction?
KEVIN HARRIS: Let's go to the first question that he's asked. “Why might one think that time has a direction to it? That seems to go counter to what physicists often say.” Maudlin says he thinks that is a little big backwards.
DR. CRAIG: Right! He says,
I think that’s a little bit backwards. Go to the man on the street and ask whether time has a direction, whether the future is different from the past, and whether time doesn’t march on toward the future. That’s the natural view. The more interesting view is how the physicists manage to convince themselves that time doesn’t have a direction.
So he says the real question is how could physicists come up with a view that is so contrary to our everyday experience. Everybody admits that the view of the common man is that time has a direction and it does involve this becoming. Maudlin seems to blame this delusion of modern physics on standard geometry. He says,
Standard geometry just wasn’t developed for the purpose of doing space-time. It was developed for the purpose of just doing spaces, and spaces have no directedness in them. And then you took this formal tool that you developed for this one purpose and then pushed it to this other purpose.
So he is saying think of Euclidean geometry – the geometry of a plane or of cubes and spheres and things of this sort. These are just talking about spatial objects, spatial geometry. And he said what physics did was pressed this spatial geometry into service in analyzing this four-dimensional geometrical object called space-time, but this is not a four-dimensional space! This is a space-time. There is one dimension of this entity that is different than the other dimensions and is unique. So he seems to think that the blame is with using geometry in this sort of uncritical way to analyze time as well as space. I think that is true. People think of time as a continuum composed of points which is stretched out at a line, and even if you add a direction to it and say one direction on the line is past and the other direction is future (or better, one direction is “earlier than” and the other direction is “later than”) you're still thinking of it as like a geometrical line which is stretched out rather than as a dynamic process of becoming.
KEVIN HARRIS: In answer to how they managed to convince themselves that time doesn't have a direction, Edwin Tse says, “They would reply that it’s a consequence of Einstein’s special theory of relativity, which holds that time is a fourth dimension.” Maudlin says, “This notion that time is just a fourth dimension is highly misleading.”
DR. CRAIG: Yes. What he goes on to point out is that even in relativity theory even though you can analyze space-time in terms of this four-dimensional geometrical structure one of the dimensions, as I say, is different. And this shows up in the equations. It has a different sign – rather than plus it shows up as a negative (minus). So even in relativity theory time is distinct from space in terms of the way in which these dimensions manifest themselves in the equations.
KEVIN HARRIS: He goes on to say a little bit later here that geometry just wasn't developed for studying this. It works in algebra, but it doesn't work in geometry.
DR. CRAIG: What he points out is that special relativity has a mathematics which is algebraic. There are algebraic equations for transforming space and time coordinates. He points out that a mathematician can say, Well, what would happen if I start putting negative numbers in for these quantities? He says that is a perfectly good algebraic question to do. You can use negative quantities.
KEVIN HARRIS: You can do it all day!
DR. CRAIG: Yeah! Or imaginary quantities. Use imaginary numbers and see what happens. He says the problem is it is not clear what that means geometrically. To use my own illustration, what could it possibly mean to talk about the lapse of two negative seconds or an imaginary hour of time? What is normal for the algebraist or mathematician is just a metaphysical fantasy when you try to translate it into reality.
KEVIN HARRIS: Next the interviewer says, “And so you are trying to allow for the directionality of time by rethinking geometry. How does that work?” He says, “I really was not starting from physics. I was starting from just trying to understand topology.” When I started to look into what topology was, Leipniz was one of the earlier developers of topology. That is the proportions of space that are perceived under continuous deformities. A shape can be stretched or bent or whatever but it maintains certain properties even though you can deform it, twist it, bend it, and things like that. So it is a study of topology.
DR. CRAIG: Topology would be the most basic fundamental primitive property of a space. Then you could lay a geometry on top of that topology to provide measurements of units. Maudlin gives an illustration here. He says,
Suppose I just hand you a bag of points. It doesn’t have a geometry. So I have to add some structure to give it anything that is recognizably geometrical. In the standard approach, I specify which sets of points are open sets. In my approach, I specify which sets of points are lines.
So he wants to begin with geometrical lines as primitives. You put down a linear structure on a set of points, and then you will develop your geometry from there. So he sees lines as in a sense more primitive than points. You begin with your linear structure.
KEVIN HARRIS: He is next asked, “Why is this kind of modification important for physics?”. Maudlin says,
As soon as you start talking about space-time, the idea that time has a directionality is obviously something we begin with. There’s a tremendous difference between the past and the future. And so, as soon as you start to think geometrically of space-time, of something that has temporal characteristics, a natural thought is that you are thinking of something that does now have an intrinsic directionality.
DR. CRAIG: This was where my antenna went up because it seemed to me that this is a non-sequitur. Let's think geometrically of space-time, this four-dimensional space-time geometrical object. And let's suppose, as he says, that it has an inherent directionality along one of its dimensions which is time. He says “a natural thought is that you are thinking of something that does now have an intrinsic directionality.” I don't see that that follows at all. When you are introducing the word “now” you are introducing into this four-dimensional reality a privileged present, that there is something that is true about this “now” rather than just saying it tenselessly has an intrinsic directionality. This may be Maudlin's surreptitiously beginning to introduce these notions of tense into his theory of the universe. That it is not enough to have this block universe that has a direction along one of its dimensions but that there are these tensed facts about it now having a certain directionality. So that's highly significant when he starts using locutions like this.
KEVIN HARRIS: He is next asked, “Physicists have other arguments for why time doesn’t have a direction.” Maudlin says, “Often one will hear that there’s a time-reversal symmetry in the laws. But the normal way you describe a time-reversal symmetry presupposes there’s a direction of time.”
DR. CRAIG: Right. I really like this point. He gives the example of the glass falling onto the floor and shattering into a thousand pieces, or of a film-reversed version of that where the pieces assemble and the glass jumps off of the floor back onto the table. He says you can do that. You can run the laws of nature either way. But he says that itself presupposes a causal directionality. He says,
. . . they presuppose that there’s a difference between the glass falling and the glass jumping, and there’s a difference between the glass shattering and the glass recombining. And the difference between those two is always which direction is the future, and which direction is the past.
So he's rightly saying that the reversibility of the laws of nature doesn't show that time is illusory or that there is no direction of time. On the contrary, it actually is presupposing and assuming that there is a difference between earlier and later. That's why I thought that the title of this article or this interview is a misnomer - “A Defense of the Reality of Time.” This isn't about the reality of time. I think this is a defense in the end of the reality of tense and temporal becoming. Unless you take the view that McTaggart did that time without tense and becoming isn't really time at all. In that sense it could be a defense of time.
KEVIN HARRIS: So he's not arguing against time being an illusion? Time being illusory?
DR. CRAIG: No. B-theorists don't think that time is an illusion. They just think that time doesn't have a direction and that temporal becoming is an illusion. But they would recognize relations of earlier than and later than along the direction of time. Adolf Grünbaum, who is a philosopher of space and time, wrote an article many years ago on the anisotropy of time in which he defended the view that time has a direction, that time is not isotropic like space. There is an “earlier than” direction and there's a “later than” direction. But Grünbaum vociferously resisted any interpretation of time as involving tense and the objectivity of temporal becoming. He was a deeply committed B-theorist or tenseless theorist of time. And Maudlin seems to be wanting to break loose from that although sometimes it sounds like his affirmations are really the same as Grünbaum's. He is just confirming the anisotropy time, and that's not sufficient to give you the common sense view of time which involves tense and becoming.
KEVIN HARRIS: OK. We'll pick it up right there next time on Reasonable Faith with Dr. William Lane Craig.