Sean Carroll and the Principle of Sufficient Reason

In my previous post on Sean Carroll’s book, The Big Picture, I discussed Carroll’s metaphysics, which seemed to come down to a radical materialism ( although that wasn’t entirely clear). As far as epistemology is concerned, Carroll, like other atheist science popularizers, takes for granted that science is the only avenue to knowledge (or the only one worth paying attention to), even though this idea is problematic in a number of different ways. Please read that post if you are interested in a refutation of Carroll’s metaphysics and epistemology. I want to focus here specifically on his comments on the Principle of Sufficient Reason, which is the linchpin of the Leibnizian Cosmological Argument or the Argument from Contingency. The Principle of Sufficient Reason ( “the Principle” or “PSR” for short) can be formulated in different ways, something which Carroll fails to take into account. The principle is not necessarily that “everything happens for a reason” or that “every fact has an explanation.” That would be a very strong formulation of the principle that is unnecessarily broad.  The version that I defend in my own summary of the argument is that the existence of all contingent things require an explanation. That is, there is a reason for the existence of all contingent things. Something that is contingent is merely something that does not exist in all possible worlds. It could have failed to exist. If it could have failed to exist, there must be something that brought it into existence. It depends on something else for its existence; some event or circumstance or process.

Judge, Jury and Statistician

Carroll begins his chapter on the Principle with the case of Lucia de Berk who was convicted of murder based on a statistical calculation (which was later shown to be incorrect). Carroll explains this miscarriage of justice in the following way: “But math mistakes alone are not sufficient to account for Lucia de Berk’s wrongful conviction. What started the ball rolling was a psychological conviction: the idea that something as horrible as these infant deaths couldn’t just be random; someone must be to blame. There must be a reason why it happened. As horrible as the death of a child necessarily is, it becomes more sensible to us if it can somehow be explained as the result of someone’s actions, rather than simply random chance.”[1] If this is meant as a counter-example to the Principle of Sufficient Reason then it does not work. There is nothing in the PSR which says that the reason why something happens must be the result of personal agency. Yes there must be a reason why all those infants died. They would have died because of the individual disease processes that killed them. With sufficient medical knowledge, you can show very clearly the reason why each of them died which means that the PSR is vindicated. Perhaps Carroll is referring to a reason why that particular number of infants died that month or that year rather than fewer or more, not merely how they individually died. What is the reason or explanation for the fact that so many infants died, rather than just the fact that they died. This is really the same question. If you know the life histories of each infant, then you will know why. It could be the result of poisoning, but it could also be that more infants came into contact with a certain pathogen that month. Why did more infants come into contact with a pathogen that month? Well, the reason why could be any number of things. Perhaps the mother did not wash her hands at a crucial moment. Perhaps a relative came to visit to hold the baby and that relative was a carrier of a particular disease without showing any symptoms. There could be any number of reasons. In short, explaining why each individual infant got sick and died is the same thing as explaining why so many infants died, because once you know in each individual case, you know by implication, why precisely that number of infants died in that month or that year. (Also, just because there isn’t a single reason why all the infants died, doesn’t mean there isn’t good reason why they died. The reason will just be different in each case. And just because there is no connection between the individual reasons for the infants’ deaths doesn’t mean there is no reason why that precise number of infants died that month.) So, Carroll’s error here seems to be the supposition that simply because something is not the result of personal agency it is therefore not a “reason why”, although he doesn’t defend this supposition, and it is not reasonable. There is also no version of the PSR which says that the explanation or reason for things needs to be personal agent. It could be a personal agent. But it might be an impersonal process. The reason why the Argument from Contingency posits a personal agent in the case of the universe is not because the Principle itself says that it must be, but because no impersonal mechanism works as an explanation for the universe as a whole. That impersonal mechanism would also be contingent, which means that it would just move the problem back one level. You require a necessary thing. You also require something that is immaterial and timeless, since matter and time come into existence with the universe. There are other reasons why a personal mind fits the profile as an explanation, which you can find in my summary of the Argument from Contingency.

What is the PSR according to Carroll?

Carroll formulates the principle as follows: “For any true fact, there is a reason why it is so, and why something else is not so instead.”[2]

As I’ve noted earlier, there are different ways to state the PSR and the version that Carroll chooses is about the strongest available “on the market”.

Everything Happens for a Reason?

He says, “Leibniz once formulated it simply as “Nothing happens without a reason,” which is remarkably close to the maxim “Everything happens for a reason,” which you can buy on T-shirts and bumper stickers today. (Alternatively, designer and cancer survivor Emily McDowell sells empathy cards reading “Please let me be the first to punch the next person who tells you everything happens for a reason.””[3] Carroll is very seriously misrepresenting the PSR by saying it is “remarkably close” to the bumper sticker wisdom that “everything happens for a reason.” Why? The saying that “everything happens for a reason” usually means that everything has some sort of mystical or supernatural reason, not a reason in general. That is no doubt the idea that Emily McDowell is responding to. It is easy to illustrate that this is what’s going on, because every person’s cancer, including Emily McDowell’s, does have a clear reason for why it happened (if you know enough about cancer). If you know enough about someone’s life histories and the carcinogens they came into contact with, and perhaps also how the first cells started reproducing abnormally that would eventually lead to their cancer, then you know the reason why they got cancer. There may be a supernatural reason in addition to the physical reasons for why someone gets cancer, but the Principle certainly doesn’t require it. So there is a reason why every single person gets cancer, and medical research into cancer is based on that fundamental assumption. Indeed, all scientific research rests on the assumption that there are “reasons why.” Like in the previous example with Lucia de Berk, Carroll has once again supposed that “reasons why” must fall into a particular class of reasons. In the first case, this was personal agency. In this case, it is some sort of mystical or supernatural reason. Second, Carroll has chosen a very strong version of the PSR which he doesn’t cite as the principle that Leibniz or other contemporary defenders of the PSR hold. He doesn’t mention that there are weaker versions of the Principle. The principle he does represent ( that all true facts require an explanation) was probably not even defended by Leibniz himself.

Empirical Support for the PSR

In the next few pages, Carroll’s strategy is essentially to say that the Principle makes sense of our daily lives, but that this doesn’t mean it is applicable beyond our daily lives.[4] What can we say in defense of the PSR? It has ample empirical support. Every situation or phenomenon we look at, there is some reason why. Indeed, science is precisely in the business of finding “reasons why” for the phenomena it studies. If you understand that at least some version of the Principle of Sufficient Reason is an assumption of the scientific method, then you will understand why the scientific method could never disprove it. This, in itself, should be enough evidence to make it very improbable that any particular thing’s existence we look at can have no explanation. Carroll’s primary response to the massive empirical support for the PSR is to say that we cannot expect it to apply to something beyond the world of medium-sized objects where we observe it all the time. Even though the Principle may work well in terms of our daily lives, we cannot expect it therefore to be a good logical or metaphysical principle. The problem with this is that you can use this same logic against every other basic principle that is used in logic, including the law of non-contradiction, the law of the excluded middle, modus ponens, modus tollens etc. Why is that a problem? All our thinking depends on logical axioms like those, including our scientific thinking about the cosmos. If you want to start saying that intuitions we form as a result of our daily life are invalid for the reason that we develop them in our interaction with the world, then you are also undermining all the other intuitions and logical axioms that are used in all our thinking. We are creatures of the world of medium-sized of objects. If the intuitions we develop in that world are invalid beyond the world of medium-sized objects, then we cannot think about the microscopic and the macroscopic at all and all our knowledge of those worlds are automatically wrong, because the intuitions we used to think about those things were all developed in our world of medium-sized objects.

Logical Support for the PSR

We also have to be clear about what we’re saying when we say that something that came to be doesn’t have an explanation in order to understand how radical a notion it is. It is not the same thing as saying that something doesn’t have a cause (which is in itself a radical notion). Something can be causeless and yet have an explanation. What is an explanation? An explanation of a particular fact or existence is just the story of how it came to be, the way it came to be that way. What determined it to be and to be that way? When you realize that something was not always this way, then there was some way that it became this way. To deny that is logically incoherent. What does it mean to say that even though something changed, there is no way that it changed? It doesn’t make sense. Similarly, if something could have had property x but has property y, what does it mean to say that there was no way that that happened? That is what you are saying when you’re saying that a contingent thing doesn’t have an explanation. If there were different ways for something to be, then there was some way it became one type of thing rather than another type of thing. This is more than an empirical principle. It is not clear what it means to say that there is no explanation for something that came to be or that could have been different. So, the PSR also has logical support. As I’ve indicated in my previous post on Carroll, the version of the PSR that I defend is logically necessary, which is to say that it is logically incoherent to deny it ( by denying it, you affirm a contradiction). To say that all contingent things require an explanation is logically necessary, because a contingent thing is something which could have failed to exist. If it could have failed to exist there is a reason why it exists. That means it depends on something for it’s existence ( some event, or mechanism or personal agent). To deny this version of the principle is to say that there are contingent things that do not have explanations. But this is like saying the following: there are some things which depend on something else for their existence that do not depend on something else for its existence. It is to affirm a contradiction. You may dispute that the fact that something could have failed to exist means that there must be some reason it exists. But trying to explain this to someone who denies it is like trying to explain to someone why the law of non-contradiction in logic is true. It is something that is apprehended intuitively like the idea that 2 + 2 = 4 and not 5. So, the version of the Principle that I’ve defended is a logical principle, not merely something we observe all the time, even though observing it all the time is more than enough support to believe it. But, you may say, if the PSR is true, then there shouldn’t be principles like the law of non-contradiction or the PSR itself, because it should then be possible to explain them. We cannot explain either of these principles. But neither of these principles exist contingently ( and we may also talk about whether it is right to talk of a principle “existing”).

Contingent Brute Facts

The best that Carroll can do as disproving evidence against the Principle of Sufficient Reason is to say that things we don’t know at the moment may not have an explanation or simply by positing the idea that some things may just be brute facts.[5] Of course, there must be brute facts, because otherwise we would have explanation upon explanation upon explanation going on forever. But that fact or being has to be metaphysically necessary ( it must not be contingent). The universe and everything in it is contingent; it could have failed to exist. Carroll really wants us to accept the idea of a contingent brute fact, not just any brute fact, which all our experience contradicts and which I’ve argued is also probably logically incoherent.

But our ignorance of certain scientific questions is not evidence against the Principle of Sufficient Reason, because there may also be an explanation. You cannot use our ignorance of certain questions as evidence against the Principle, because then you are merely assuming that our ignorance is not really ignorance at all. But you are assuming that without any reason. How would you show that it is not ignorance but just brute fact? You can’t, which shows how fundamental these concepts are in metaphysics. But this also highlights how anti-scientific a denial of the Principle is. If you believe that the Principle is not true, then you would be more likely to assume that when you reach a road block in your research that this may just be a brute fact and give up. But it also may just be ignorance and you just don’t have the technology to investigate it or there’s some other gap in your knowledge that is preventing you from understanding it. In fact, no matter how many brilliant scientists try their hand at explaining something, you can never show that it is a brute fact, because there is no guarantee that human minds can even understand the whole universe. We have no way of judging the probability that human minds are capable of understanding the universe as a whole and everything about how it functions. In summary, the idea of a contingent brute fact then is indefensible. It is impossible to establish with even reasonable confidence that something is a contingent brute fact, because all our experience counts against it, it is logically incoherent, and it is impossible to support it empirically, because you can never show that whatever question we don’t have an explanation for is really a brute fact rather than a display of our own ignorance. This means that it is a dead-end in as a refutation of the Principle.

The Wider Context

Another objection Carroll levels at the Principle is that the PSR makes sense within a context, but we cannot ask about the reasons for the universe and the laws of physics, because there is not necessarily any wider context. “But the universe, and the laws of physics, aren’t embedded in any bigger context, as far as we know. They might be — we should be open-minded about the possibility of something outside our physical universe, whether it’s a nonphysical reality or something more mundane, like an ensemble of universes that make up a multiverse.”[6] But this doesn’t make sense as a response. You cannot respond to the claim that something requires an explanation by essentially saying that we don’t know it has an explanation. The claim is precisely that it requires an explanation, which means saying that we don’t know it has an explanation is to presuppose that you are right that the Principle of Sufficient Reason is wrong and therefore to argue in a circle. Clearly, before we explained something we don’t know what explained it, and we didn’t know that there existed something that could explain it, but the fact of not knowing what explains something doesn’t affect whether or not it requires explanation. If we know that something logically requires an explanation and we don’t know if there is anything beyond the universe, then the fact that it requires explanation implies that there is something beyond the universe. So this doesn’t really respond to the PSR at all.


[1] Carroll, Sean, The Big Picture, (New York: Dutton, 2016) p. 39

[2] Ibid., 40

[3] Ibid., 40

[4] Ibid., 41-44

[5] Ibid., 40,45

[6] Ibid., 45

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