Are Fine-Tuning Arguments for God (or the Multiverse) Circular?
In a recent video, theoretical physicist Sabine Hossenfelder argues that design arguments for God’s existence commit the fallacy of begging the question—also known as circular reasoning.
Before we began, I want to lay my cards on the table and say that I’m a fan of Sabine Hossenfelder. She’s smart, well qualified, and a research fellow at the Frankfurt Institute for Advanced Studies.
I appreciate her commitment to explaining physics in comprehensible terms and her willingness to challenge ideas that are fashionable in the physics community but that are not well supported by evidence.
She also doesn’t reject religious claims out of hand—as many do. Instead, she typically concludes that they are beyond what science can tell us, one way or the other.
A Finely Tuned Universe?
In her recent video, she notes that many people argue that the laws of physics that govern our universe seem finely tuned to allow life to exist. Even slight changes in the constants they involve would prevent life from ever arising.
An example she cites is that if the cosmological constant (i.e., the energy density of space) were too large, galaxies would never form.
Similarly, if the electromagnetic force was too strong, nuclear fusion would not light up stars.
Given all the values we can imagine these constants having, it seems unlikely that the laws that govern our universe would be finely tuned to allow life to exist just by random chance, so the question is how to explain this.
God or the Multiverse?
One proposed explanation is that the universe isn’t finely tuned by chance. It’s finely tuned by design.
Some entity with immense, universe-spanning power (i.e., God) designed the universe to be this way, and in religious circles, this type of argument is known as a “design argument” for God’s existence.
Another proposed explanation is that our universe is finely tuned for life by chance. But since it would be improbable to get a finely tuned universe with a single throw of the dice, it’s inferred that there must be other throws of the dice.
In other words, our universe is just one of countless universes that contain other laws and constants, and we just happen to be living in a universe where the things happen to come up right for life to exist.
(After all, we wouldn’t be here if they didn’t.)
Such a collection of universes is known as a multiverse.
God and the Multiverse?
From a religious perspective, the multiverse hypothesis can look like an attempt to get around the obvious implication of the universe’s apparent design—i.e., that it has a Designer.
However, that doesn’t mean that the multiverse doesn’t exist. If he chose, God could create a vast array of universes, each of which have different laws, and not all of them may contain life. (After all, most of our own universe does not contain life!)
Similarly, from the perspective of someone who believes in the multiverse, multiple universes wouldn’t rule out the existence of God, because you could still need a God to explain why the multiverse exists at all.
The God hypothesis and the multiverse hypothesis thus are not incompatible.
Both Are Possibilities
Dr. Hossenfelder acknowledges that both God and the multiverse could be real, but she says—correctly—that this would not add to our knowledge of how our universe works.
If God exists, that doesn’t tell us what the laws of our universe are. We still have to discover those by observation.
And if the multiverse exists, that also doesn’t tell us about the laws of our universe. Observation is still necessary to figure them out.
Her claim is that the fine-tuning arguments for both God and the multiverse don’t work—and, specifically, that they involve circular reasoning.
She fleshes out this claim along the following lines:
- To infer God, the multiverse, or anything else as the cause for why our universe seems finely tuned, you need evidence that our universe’s combination of constants is unlikely.
- However, the only evidence we have is what we have measured, and—precisely because the constants are constant—we always see them having the same values.
- Therefore, we have no evidence that the combination we see is unlikely.
- So, advocates of these views must assume what they need to prove—that the combination is unlikely—and that’s circular reasoning.
The Pen Objection
Dr. Hossenfelder seeks to head off an objection to her argument by pointing to a parallel case: Suppose you saw an ink pen standing upright on a table, balanced on its point.
It seems very unlikely that a pen would be balanced in this way, and so you’d suspect there was a reason why the pen was standing like this—perhaps a special mechanism of some sort.
But, she says, the reason that we can rationally suspect this is because we have experience with pens and know how hard it is to balance them this way.
Therefore, it would not be circular reasoning to propose an explanation for the oddly balanced pen.
However, the only experience we have with the constants of nature is the set we see. We thus can’t estimate how likely or unlikely they are to occur, because we don’t have evidence about the probability of this combination of constants.
What Do You Mean by “Evidence”?
The problem with Dr. Hossenfelder’s argument is the way she uses the term “evidence.”
In the video, she seems to assume that “evidence” must mean empirical evidence—that is, evidence derived from observation using the physical senses (and their technological extensions, like radio telescopes and electron microscopes).
This is the kind of evidence used in the natural sciences, and so you also could call it “scientific evidence.”
However, this is not the only kind of evidence there is.
Fields like logic, mathematics, and ethics depend on principles—sometimes called axioms—that cannot be proved by observation.
The evidence we have for them comes in the form of intuitions, because they seem either self-evidently true or self-evidently probable to us.
Since each of these fields is part of or closely connected with philosophy, we might refer to this intuitive evidence as “philosophical evidence.”
Whatever you want to call it, it’s evidence that we depend on—certainly in every field that involves logic, mathematics, and ethics.
Science involves all three, and so, while the scientific enterprise depends on observational evidence, it also depends on intuitive, philosophical evidence.
Do We Lack Observational Evidence?
It’s true that we can’t observe other universes, and so we lack observational evidence of the laws and constants that might be at play in them.
But does this mean that we lack any observational evidence that constants could have different values?
Confining ourselves strictly to our own universe—the only one we can observe—we see that not all constants have the same value. For example:
- The strong coupling constant is about 1
- The fine-structure constant is about 1/137
- The top quark mass is about 1/10^17
- The bottom quark mass is about 3/10^19
- The electron mass is about 4/10^23
Clearly, we see things that we regard as constants with different values, even in our own universe. The constants I’ve just listed span 23 orders of magnitude!
Why do all these dimensionless constants have different values?
That’s a natural question to ask!
And so, one could argue that we do have observational evidence that constants can have different values—not from universe to universe but from constant to constant—and that leaves many people asking why.
Further, we even have evidence that some of these constants may vary over time.
Dr. Hossenfelder says in her video that this “has nothing to do with the fine-tuning arguments,” but this seems false.
If we have evidence that some things scientists initially took as constants aren’t constant after all, then it further raises the question of why they have the values they do.
The Evidence of Intuition
I’m not at all convinced that we don’t have observational evidence that invites us to ask why the constants we see in our universe have the values they do.
However, even if I were to waive this point, we still have one other line of evidence: direct intuition.
People who study the constants can imagine them having different values. We can, for example, imagine the electron mass being twice—or half—what its measured value is.
That makes it rational to ask why a constant has the value it does. As theoretical physicist and Nobel laureate Richard Feynman famously said about the fine-structure constant:
It has been a mystery ever since it was discovered more than fifty years ago, and all good theoretical physicists put this number up on their wall and worry about it.)
Immediately you would like to know where this number for a coupling comes from: is it related to pi or perhaps to the base of natural logarithms? Nobody knows. It’s one of the greatest damn mysteries of physics: a magic number that comes to us with no understanding by man. You might say the “hand of God” wrote that number, and “we don’t know how He pushed His pencil.” We know what kind of a dance to do experimentally to measure this number very accurately, but we don’t know what kind of dance to do on the computer to make this number come out – without putting it in secretly!
In Search of Explanations
Finding out the explanations for things is a key part of the scientific enterprise. The same is true of the philosophical enterprise.
We have a powerful (philosophical) intuition that things we encounter have explanations, and thus we seek them.
In philosophy, this intuition is sometimes framed as the Principle of Sufficient Reason, and while precisely how to formulate the principle is controversial, some kind of sufficient-reason quest is behind the scientific enterprise.
It would not do at all—and it would not be scientific at all—to encounter phenomena like stars shining, plants growing, and objects falling and say, “Those are just brute facts that don’t have explanations.”
Our intuition tells us that they need explanations, and it is the task of science to find them—to the extent it can—based on observation of how they work.
When we discern that many of these phenomena can be explained in terms of a set of underlying laws and constants, it’s then natural to ask what the explanation for these is—particularly when we notice that if these things were even slightly different, we wouldn’t be here.
The Limits of Science
Ultimately, Dr. Hossenfelder doesn’t deny that explanations for these things exist. She specifically says:
But this does not mean god or the multiverse do not exist. It just means that evidence cannot tell us whether they do or do not exist. It means, god and the multiverse are not scientific ideas.
The problem with this is how she’s using the word “evidence.” She’s taking it to mean empirical/observational/scientific evidence.
And it’s true that, at least in any conventional sense, you can’t do a laboratory experiment that shows that God exists—or a laboratory experiment that shows the multiverse exists.
Consequently, both ideas are beyond what can be proved scientifically.
But that doesn’t mean you can’t argue for them on other grounds. You can, in fact, argue for them based on your intuitions about what needs to be true in order to explain the constants as we see them.
This makes God and the multiverse subjects of philosophical argumentation rather than scientific demonstration.
Not Circular Reasoning
And that means that the charge of circular reasoning is false.
It would be circular reasoning to simply assume that it’s improbable the values of the constants we see in our universe should have the values they do.
But it’s not circular reasoning to say, “I have a strong intuition that this calls for an explanation” and then reason your way to what you think best explains it—even if that explanation lies beyond what’s scientifically measurable.
In other words, just because you’re doing something beyond science, it doesn’t mean that you’re simply begging the question.
The Return of the Pen
Let’s apply this insight to the ink pen example that Dr. Hossenfelder brought up.
Even if I’d never before seen a pen–or any similar object–it would make sense, when I first encountered one, for me to ask why it is the way it is.
Just like scientists and philosophers ask this for anything else they encounter.
I don’t need to know how likely or unlikely it is that an ink pen would be balanced on its point. The fact I can conceive of it being otherwise makes the question of why it’s standing rational.
Just asking the question is not begging the question.
And neither is having an intuition that it’s unlikely to be standing on its point (or in any other position) without an explanation.
Tying up Loose Ends
To keep things simple, I haven’t responded to everything Dr. Hossenfelder says in her video, since I wanted to keep things focused on her main argument.
However, I would like to circle back to the God hypothesis and the multiverse hypothesis as explanations for the apparent fine-tuning of our universe.
Personally, I like the idea of there being multiple universes—not for scientific or philosophical reasons, but just because I think it would be cool.
I’d also be fine with them having different laws and constants governing them. That would only add to the coolness.
But—speaking philosophically—there would still need to be a reason why the whole collection of them exist and why the laws that govern them vary from one to another.
Elsewhere, I’ve written about this as a “cosmic slot machine”:
If there is a multiverse with every possible combination of natural laws in the universes it contains . . . what is driving the change of laws in each universe? If there is a cosmic slot machine, whose innards cause the constants to come up different in each universe, why is that the case?
To explain the existence of such a cosmic slot machine, we’d need to appeal to something beyond the multiverse itself.
And so, whether or not there is a multiverse, I favor the God hypothesis.
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