The four-dimensional block universe, supported by Einstein’s theory of relativity, is a world where past, present and future are equally real. Philosophers of time have debated about whether this makes a difference to issues like freedom, responsibility, and death. Arguing against the hopeless fatalism often associated with this theory, Nikk Effingham examines the philosophical details of the block universe and whether it truly affects our human experience.

Taffy Brodesser-Akner’s Fleishman is in Trouble is now a Hulu-filmed drama series. In it, Toby’s nine-year old son asks him about the block universe. ‘It’s a theory,’ Toby says. ‘It’s this idea that, like, all of life is happening at the same time. Like all points of existence are, I don’t know, occurring simultaneously.’ Weird as that theory may sound, it is now mainstream thinking for physicists and philosophers. You might believe, as the characters of Fleishman tacitly do, that the block universe is a meaningful and important theory—that, if it were true, we should see ourselves, our lives, and the lives of others very differently because of it.

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What is the block universe?

Toby is hesitant in pinning down the details of the block universe—and rightly so, since it’s a complicated view to get your head around. The underlying idea is that time is like space. When it comes to space, we readily believe that places that aren’t ‘here’ are nevertheless real. Whilst I am in the United Kingdom, that doesn’t mean that France or Mongolia or Pluto don’t also exist. So, if time is like space, then times that aren’t ‘now’ exist. Dinosaurs roaming the Earth and the Battle of Hastings might not be currently happening but, if the universe is a block, that doesn’t mean they aren’t real. Given the block universe theory, those things exist, although they are removed from us, albeit in time instead of space. The same goes for the future: every future event that will ever come to pass is as real and existent as anything you see around you right now. My not knowing what will come to happen is basically the same as me not knowing what Julius Caesar’s shoe size was—it is a failure of knowledge, not of a failure of reality to have fixed the facts.

You might think that this sounds nuts. But this idea that the past and future are as real as the present has been around for a long time. Moreover, it became academic orthodoxy around the time of Albert Einstein, whose theory of relativity is often read as saying that the universe is a block.

Fatalism: Is the future as unchangeable as the past?

It’s not hard to see why we might believe that the block universe has radical ramifications on how we live. Imagine it is true that I will get a divorce in 2033. Given the block universe, it’s true—right now! —that I will get a divorce in ten years’ time. So how can I avoid it? If it’s true—right now! —that I’ll get a divorce, how can I change that fact? (Equally, if I won’t get a divorce then I don’t have the power to get one, which is just as unintuitive and strange!)

Compare to what we say about the past: the past is already done and dusted; since we don’t have time machines, we have no power to affect the past. The suggestion is that the same applies here: if the future exists already, it too is done and dusted, and we have no power to affect the future either. Call this view ‘fatalism’.

The fatalist view is as radical as it gets! No-one would be responsible for anything that they do. From the smallest error of judgement to the greatest crimes of genocide, given fatalism everyone is powerless to prevent what goes on around them. If we are all powerless, then no-one is responsible for how they act, whether for good or bad. We should forgive those who have done even the most heinous of things; equally, we shouldn’t bother praising anyone who makes any great sacrifice. (Although, if you fail to forgive people, don’t feel bad—given fatalism, you didn’t have any choice in the matter!)

Fatalism, if true, would be exceedingly revisionary. But does the block universe mean that it is true?

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My not knowing what will come to happen is basically the same as me not knowing what Julius Caesar’s shoe size was—it is a failure of knowledge, not of a failure of reality to have fixed the facts

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Against Fatalism

It is popular amongst philosophers to think that there is something flawed with the above reasoning. Whilst there is something to the sentiment that I cannot change the future anymore than I could change the past, philosophers tend to believe that this is less surprising than it sounds.

Consider changing the past. Imagine I had an acrimonious break-up with an ex-girlfriend twenty-five years ago. Since I cannot change the past, then there is nothing that I can do to stop that. But whilst I might not be able to do anything about that now, what is salient is that I could have changed how the past was back then. Back in the 90s, when I was presently dating my girlfriend, I could have done something to avoid the bitterness even though—in point of fact—I failed to do so.

Consider changing the future. Given the universe is a block, the future is as unchangeable as the past, but only in the sense that if I am to get divorced in 2033 then I am powerless to prevent that right now. That is: Sat here in 2023, I can no more press a magic button to stop me getting a divorce in 2033 than I could wave a magic wand to change how I dated back in 1998. But that powerlessness isn’t a relevant powerlessness. What is relevant is that, when the future rolls around, I will have the power to change things—and isn’t that what counts? When it is 2033, it will be in my power to avoid the caustic arguments that lead to me divorcing my wife, just as it was in my power to avoid similar arguments with my girlfriend back in 1998. I am unable to stop those bitter arguments right now, but this does not undermine the more important point that I will be able to stop them in the future. And clearly, it’s that latter sense of having the power to stop arguments that is what really matters.

Is the future inevitable?

You might think that I haven’t quite scratched the itch that you had about why block universe is so mind boggling. You would be in good company—not every philosopher agrees with the argument I’ve just presented. So, consider another argument for fatalism on the back of the block universe. Assuming I will get divorced in 2033, then (given the block universe) it is true right now that I am getting divorced in 2033. Thus, if I did anything to avoid getting divorced, it’d be both true that I get a divorce in 2033 and false that I get the divorce—a contradiction! The argument for fatalism says that, since I don’t have the power to bring about that contradiction (anymore than I could prove that 2+2=5 or that I could get a 3D printer to churn out spherical cubes) then fatalism is true.

But I suspect that this argument is also flawed. It conflates what will be the case with what must be the case. Compare it to talk about the past. Facts about what was the case can be true without us thinking that they had to be that way. Imagine a criminal stole some jewels and, appearing in court, he admits it. Nevertheless, he says he is innocent. His defence is this: because it is true that he stole the jewels, it follows that he had to steal the jewels; since he had to do it, it’s not his fault.

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That’s a ridiculous defence to make—just because he did it does not mean that he had to! Similarly, we should deny that we can move from the fact that I will have a divorce to the (much stronger!) claim that I must get a divorce, or that I have no power over whether I get divorced, or that I bear no responsibility for the bitter arguments that lead to my divorce.

Death

There have been other proposals, apart from fatalism, about how the block universe may matter to how we live. Following the death of his friend, Michael Besso, Einstein wrote the following to his widow:

Now he has departed from this strange world a little ahead of me. That means nothing. People like us, who believe in physics, know that the distinction between past, present and future is only a stubbornly persistent illusion.

For Einstein, Besso hasn’t gone anywhere. Besso still exists; he has not ceased to be, as one might naturally fear happens after death. It is merely that Besso is no longer near Einstein in spacetime. Einstein is saying that the block universe offers us comfort, that death need no longer be as saddening as we once thought.

But I think Einstein’s reasoning is wrong-headed. He makes it sound like death is a one-way trip that you never return from. In a sense, that’s true—but isn’t that reason enough to be upset? If a loved one leaves me—never to return, never to send an email or a text, never again for us to see one another—that is a cause for great sadness.

Of course, this sadness might not be as great a sadness as I would feel had you died. If your one-way trip takes you somewhere wonderful, then—whilst I might be sad at your leaving—I would not be as sad as if you had been killed. In that case, the trip is bad for us, but it is not bad for you. So, you might think that Einstein at least ameliorates some of death’s sadness by consoling us that, given the universe is a block, Besso’s death is not as bad for him as you might otherwise have thought.

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The block universe is a theory for physicists and not psychiatrists, a thesis for philosophers and not therapists

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Even here, though, I think this is the wrong lesson to draw. Even once we allow that the block universe theory says that Besso (in some sense) continues to exist after his death, it is not a sense from which we should draw any comfort. Imagine my loved one goes on a one-way trip but is also cryogenically frozen for all eternity; they never cease to exist, but they are no longer living their life, and no longer living out their dreams. That seems to be exactly as bad for them as if they had died. It makes little difference whether you spend an eternity in the grave or an eternity in the cooler—the mere continuation of your existence is not, itself, any comfort. What we have when we are alive, but lose when we are dead, is a chance to continue to pursue our goals. If you take a one-way trip to a wonderful place, I can take solace that you are still flourishing, in a way that I cannot if you are cryogenically frozen; similarly, we should take no solace if, as the block universe theory says, you continue to exist but are forever locked within the amber of the past.

Overall, then, the block universe theory makes less of a difference to how we live our lives than some people have thought. The block universe is a theory for physicists and not psychiatrists, a thesis for philosophers and not therapists. The characters of Fleishman need not have troubled themselves about it—and nor either should you.