Sunday, April 1, 2018

The Metaphysics of Time

Let's suppose that you slip and spill a cup of coffee all over yourself right now, and that you also spilled a similar cup last month, and that you will again next year. Of these three events, the present spill is so much more vivid, isn't it? That is a principal reason why metaphysicians called presentists say that if anything is physically real, then it exists now. Advocates of the growing-past theory of metaphysics argue that, although that past cup of coffee is less vivid, nevertheless it is just as real. It simply is not present. The past grows, they say, by accumulating more objects and events. Those past cups of coffee are real because they once were present. Future cups are unreal, though, because they have never been present.

Opposed to both presentism and the growing-past theory, the metaphysical theory of eternalism implies that all future cups of coffee are just as real as the present and past ones. Presentism is the metaphysical position that is closest to common sense. It is the position that was adopted by most philosophers before the confirmation of the theory of relativity, yet now eternalism is the most popular position.

The debate is about physical time, the time that clocks are designed to measure. It is not about psychological time, the awareness of physical time.

Opponents of presentism complain that it cannot account for causation, for April showers causing May flowers. Can there be causation without both the cause and the effect being real?

Regarding eternalism and its acceptance now of the reality of the future, the philosopher William James famously remarked that the future is so unreal that even God cannot anticipate it. The eternalist counters that not being anticipated doesn't imply not being real.

The eternalists' primary argument is that the distinctions among past, present, and future are not reflected in the laws of physics and so are merely subjective, depending on whose perspective is being assumed. Regarding these perspectives, your birth is in your past, but it is in George Washington's future. So, at least some of George Washington's future is real. If some, why not all?

The cup of coffee being handed to you here is no less real than a cup of coffee far away in Antarctica. Distance is not a mark of unreality. Similarly, a temporally distant cup of coffee is no less real than the cup you are having now, says the eternalist. Temporal distance is not a mark of unreality. The concepts of being here, being there, being present, being past, and being future are all subjective because they depend for their reference upon the situation of the person using the concept. The concepts do not signify any difference in what is objectively real.

Don't we all fear impending doom? But according to presentism and the growing-block theory, it should be irrational to have this fear since the doom is known not to be real. The eternalist defends our rationality.

A key feature of eternalism is that events are fundamental; three-dimensional objects are not. One interesting implication of this is that fundamentally you as a child, you as a teenager, you as an adult, and you (hopefully) as a very old person are not periods of the same 3-dimensional person but rather are different parts of the same 4-dimensional person, the real you. In ordinary discourse, it is usually helpful to think of persons and coffee cups as 3-dimensional, but fundamentally they are not. They are temporally extended events.

What propels philosophers and scientists toward eternalism is their belief that it is implied by the best understanding of physics. If we trust the physics, we should trust its metaphysical implications, they would say. Reality is not what it seems. Einstein adopted this position when he said, after the confirmation of his relativity theory:

It appears therefore more natural to think of physical reality as a four-dimensional existence, instead of, as hitherto, the evolution of a three-dimensional existence.

In criticism of both presentism and the growing-past theory, the eternalist asks, "Whose present is the real present?" If my present and your present are different, could one be real and the other unreal? Surely not. Now consider the implication of what you just agreed to. Relativity theory implies that which set of events counts as the present is relative to the observer's reference frame. If I move fast relative to you, then a distant event on Jupiter can be present in your frame and still five minutes in the future in my frame. These last remarks radically violate common sense. So much the worse for common sense, Einstein would say; common sense is too often the faulty product of limited experience. If the presentist and the advocate of the growing-past theory imply that the Jupiter event is not real for me, being in my future, doesn't this imply there is a problem with presentism and the growing-past theories?

These are the eternalists' main reasons for their eternalism. Presentists and advocates of the growing past have heard the reasons, yet they do not crawl away into metaphysical obscurity.

One counterargument to eternalism is from H. A. Lorentz who said that merely because relativity theory implies that any reference frame is legitimate and that nobody's present is better than anyone else's, the theory could be mistaken. Somebody's frame might still be the privileged one. Scientific theories have their limits. The philosopher A. N. Prior added that perhaps Einstein's theory shows only that we cannot know which distant event on Jupiter is simultaneous with one of our present events.

Opponents of eternalism often complain that Einstein's block of past, present, and future events is too static. It just sits there. Yet change is very real. It is the essence of time. So, there is clearly something lacking in the eternalists' block perspective, and it should not be our guide on important metaphysical issues. In response, one eternalist said, "What? Do you want the block to wiggle?"

Brad Dowden
Philosophy Department
Sacramento State University


  1. Relativity is not a doctrine. It's a physical theory that Einstein wrote in a way that can be tested, and was tested, and passed the test. So if what you conclude from it is untestable, you must have misunderstood not only what Einstein meant when he wrote it, but also what the physicists after him meant when they tested it.

    How physicists can study a physical theory and conclude that it implies an article of faith, like the block universe, is an example of the sorry state of the physics community nowadays.

    Relativity says that physical laws remain the same when a reference frame changes, defines with exact math what each of these phrases mean, uses math to find laws of motion that satisfy this constraint, and postulates that the universe follows these laws.

    In other words, it doesn't say that the universe lacks a distinction between different reference frames. It says that the distinction is there but everything moves so as to exactly counteract it.

    1. My own view is that science has metaphysical implications. I detect in between the lines of your comments that you are unhappy with drawing implications from science that are "untestable," as if we can say science is testable and metaphysics is not, so the two fields should stick to their own territory. When you say, "Relativity is not a doctrine," I understand that to mean Einstein's theory of relativity is not a metaphysical doctrine. Perhaps you mean also to imply that relativity theory is not the proper kind of thing to be drawing metaphysical implications from. These comments raise the issue of the proper relationship between science and metaphysics, and they raise the issue of what counts as being an improper methodology for doing metaphysics. My own recommendation is that metaphysics informed by science is better than metaphysics uninformed, and that there is an under-determination of metaphysics by science.

  2. Hey Professor Dowden,

    Hopefully all is well with you :).

    Do you think that quantum theory has had any implications for the eternalist position specifically? Have there been any fundamental modifications to the theory to account for the kinds of weird possibilities present to quantum accounts of nature?

    Thank you very much,
    Stan Lovelace

    1. Stan,
      I believe eternalism is consistent with all the "weird possibilities present to quantum accounts." Do you have any ideas on why eternalism might not be consistent with QM?

    2. I don't really understand QM enough to say anything that isn't extremely speculative. Anything I say could as easily be my misunderstanding of the literature.

      But, that being said, I'll see if I can still say something coherent.

      I've heard that work in Quantum Thermodynamics and Statistical Mechanics might have implications that the 2nd law is merely the apparent result of the facts about state changes taking place at the micro or quantum level. The state changes are probabilistic, and have options to evolve in ways that would violate the 2nd law (they just become more and more unlikely as you compound time and amount of interactions). Options which are closed off in the classical by the 2nd law seem to not be as strictly closed off to the quantum level - such as starting down a state change chain for a step, backtracking, and going down another side (again, I've been spoonfed popular science literature).

      If these kinds of things are 'actually' possible, does the block theory have the tools to account for them? Surely these things are epistemically closed to us at the macro scale, but if we know they can (or even do) at the micro scale what does our metaphysics say about them?

    3. Quantum Thermodynamics does allow for the possibility of phenomena that are not allowed by more classical physics, but I am confident our ontological debate about eternalism vs. growing-past vs. presentism is not affected by this.

  3. Brad, do you think it is possible to frame the debate between eternalists and presentists without using the word 'real?' My suspicion is that it is largely a battle over the right to use that word, in much the way that so many disputes in epistemology are about the right to use the word 'knowledge,' each being understood to indicate something that ought to be regarded as the supreme good.

    If, for example, the presentist just means by 'real' 'that with which I can currently perceive or interact with' and the eternalist means something like 'the structure of the universe according to our best scientific theories,' then we could simply acknowledge that yes these are two very important things and also two very different ways of using the word.

    I'm guessing the answer might be something like what you suggest above, viz., that both agree that whatever 'real' means, it should not be something that is just relative to the individual. But it seems to me that the presentist does not need to accept this. She could say that her use of the term implies that reality is in fact relative to the individual, or to groups of individuals in the same reference frame.

    Another way to discuss this might be in terms of Sellars' distinction between the manifest and the scientific image. Perhaps the presentist use of the word 'real' is more appropriate to the manifest image and the eternalist sense is more appropriate to the scientific image. Then this debate resolves into a more general one about how to understand the existence of things like persons, pictures and parentheses, which seem to depend on mutual belief.

    1. Randy,
      Yes, the debate between presentists and eternalists is a debate that can be clarified by saying the presentists generally promote the manifest image, the more commonly used image of the world, whereas the eternalists generally promote the scientific image, the image of the world as highly informed by science.

      The battle between presentists and eternalists is a battle over whose use of the word "real" is the correct one, as you say, but rarely would a presentist or eternalist say their dispute is MERELY a semantic one. Presentists usually say two events can be "really" simultaneous, regardless of reference frame, so there is an error somewhere in Albert Einstein's 1905 theory of relativity, or they may say Einstein's mathematical physics is correct but Einstein and others have misinterpreted it.

      Opposed to the scientific image of time, the famous French philosopher Henri Bergson claimed time eluded mathematics and science. During a famous public debate with Bergson in 1922, Einstein defended his own scientifically-informed treatment of time and said the time of Bergson is an illusion.

      The Continental philosopher Martin Heidegger remarked that he wrote Being and Time in 1927 as a response to this conflict.

  4. Brad, thanks for that. From your post I get the idea that the issue between presentists and eternalists is only partly about whether there is an absolute sense of simultaneity. It seems like the fact that science says there isn't weakens the case for presentism, but even if simultaneity were absolute (i.e., even if the Newtonian framework were correct) science would have no particular use for a notion of the present, and there would be no particular reason to regard the present as more absolute then the past or the future. Am I wrong about that, or do you think presentism is plausible within the Newtonian paradigm?

  5. Randy, you are right that, even if Newton's theories were correct, the proper metaphysical conclusion is that the present is not privileged ontologically. It's just that relativity theory makes this easier to appreciate.

  6. I have a question about this:

    "The concepts of being here, being there, being present, being past, and being future are all subjective because they depend for their reference upon the situation of the person using the concept. The concepts do not signify any difference in what is objectively real."

    Does this imply that the concepts of past, present, and future (not just the reality of objects existing in the past, present, and future) do not signify anything objective? If that isn't implied, would you explain why not?

    If it is implied, some of the claims you attribute to eternalism seem odd. For example, in what sense is time a dimension, if there is no objective sense in which something is past, present or future? It can't be an objectively real dimension, so talking about myself as a four-dimensional entity seems to be a merely subjective tool that gets reality wrong.

    Are there any time-claims that coherently get objective reality right? Since being subjective doesn't mean being unimportant, it seems like the presentist or growing-past advocate can accept the eternalist's position, then ignore it as they get back to more important time-sensitive issues.

  7. Bob,
    Yes, the concepts of past, present, and future do not signify anything objective.

    Saying the event of Lincoln's death is past is not an objective remark. What is objective is that Lincoln's death occurred after Julius Caesar's birth, and before your writing in this philosophy department blog.

    Time is an objectively real dimension, but the past is not an objectively real dimension. Time is, of course, not a dimension of space; it is a dimension of space-time.