A GUIDED JOURNEY
The Fine Tuning Argument for God
For most of history, people looked to religion or philosophy to think about the big questions—like where the universe came from, why it exists, and whether there’s a higher purpose behind it all. But in recent times, science—especially physics—has entered the conversation in a surprising way.
Modern physics has uncovered something deeply mysterious about the way the universe works. At first, it looked like science was well on its way to explaining how everything works. But then, scientists ran into something unexpected—something that raised a whole new kind of question. And surprisingly, the solution to this question brings us into the kind of discussions that usually belong to religion or philosophy.
In this essay, we’ll present a unique formulation of the fine tuning argument that begins with a great mystery and naturally leads to the recently discovered solution known as fine tuning. And we’ll see how it leads to one of the most fascinating arguments for the existence of God—an argument that comes straight from the frontiers of physics.
This essay discusses:
by Elie Feder and Aaron Zimmer, cohosts of the Physics to God podcast
For all these points in more depth, watch or listen to Season 1 of the Physics to God podcast, cohosted by Elie Feder PhD and Aaron Zimmer, on YouTube, Spotify, or Apple Podcasts.
The Basics: Fundamental Physics, the Constants, and a Theory of Everything
To understand the mystery, we need to know three important ideas:
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Fundamental Physics: This is the study of the most basic building blocks of everything. Tiny particles like electrons make up all matter, and they follow simple laws of nature like gravity.
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Constants of Nature: These are fixed numbers that describe things like how heavy particles are or how strongly they interact. Scientists didn’t make them up or derive them from any equation—they just measured them. Two examples are the mass of an electron and something called the fine-structure constant, which affects how strongly two electrons interact.
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Theory of Everything: Scientists have long dreamt of finding one extremely simple and elegant law that explains everything in the universe—from atoms to galaxies. This would be the one final equation explaining everything in nature. Nobel Prize-winning physicist Steven Weinberg wrote all about this pursuit in his well-known book, Dreams of a Final Theory.
Feynman’s Great Mystery: Why These Numbers?
So here’s the mystery: Why do the constants of nature have the exact values they do? Why is the fine-structure constant something weird like 1/137.035999139 instead of just 2 or 10?
Let’s think of it like a moral code that includes a rule for giving charity. If someone told you, “Give exactly 13.743627% of your money to charity,” you’d say, “That’s oddly specific!” It wouldn’t seem like a natural or reasonable number.
That’s what the constants of nature are like—super exact and kind of random.
Scientists had two possible ideas to explain them, but neither of them was very satisfying:
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Maybe the constants are just brute facts of nature, with no deeper reason behind them. But that would make the “theory of everything” less like one simple, elegant law and more like a long, messy list of weird numbers no one understands. This would be like suggesting that 13.743627% is an unexplained brute fact in your moral code. Not very satisfying.
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Maybe there's a deeper law that explains why the constants have these values. That sounds nice—but how plausible was it that physicists could find one simple law that could produce 25 exact numbers, down to the last decimal point? Scientists couldn’t even crack a single number, let alone all 25 of them!
This would be like saying, “All the rules of morality come from one simple rule: Treat others the way you want to be treated.” That’s elegant. But since the rules also say, “Give exactly 13.743627% of your money to charity,” it’s hard to see how that specific number could possibly come from the simple rule. The same thing happens in physics. The constants seem too messy and too exact to be derived from a simple, deeper theory.
Nobel Prize-winning physicist, Richard Feynman, really spelled out the mystery in his 1985 book QED (page 127). Listen to what he wrote about the fine structure constant:
It has been a mystery ever since it was discovered more than 50 years ago, and all good theoretical physicists put this number up on their wall and worry about it. Immediately, you'd like to know where this number for a coupling comes from?…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 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.
Notice that the mystery has nothing to do with fine tuning—you can see that clearly because fine tuning hasn’t even been mentioned yet!
So the great mystery remained: Why these random numbers?
What is the "God of the Gaps" Mistake?
At this point in the story, it would have been totally wrong to say, “We don’t know why the constants have those values—so God must’ve chosen them,” While that might feel like an answer, it’s actually an argument from ignorance that’s known as the God of the Gaps fallacy. It means filling a gap in our knowledge with “God” instead of admitting, “We don’t yet know.” (Feynman didn’t literally mean it when he said “the hand of God wrote that number.” He was just describing what it looked like.)
In cases like this, it’s better to keep searching and see if science can figure it out. When Feynman wrote about the problem in 1985, scientists were still hoping to find some clue that would help solve this great mystery—and that’s exactly what happened!
The Turning Point: The Discovery of Fine Tuning
Beginning in the 1980s, and maybe even a little earlier, scientists made a series of surprising discoveries about the constants of nature. While they might not seem important for physics alone, the constants turn out to be absolutely essential for things like chemistry, astronomy, and biology. If some of these 25 numbers were even a little bit different, atoms wouldn’t form, stars wouldn’t shine, and life could never exist.
This is called fine tuning. It means the constants are set with incredible precision—almost as if someone carefully adjusted them to make everything in the universe work just right.
Many examples of fine tuning were discovered. One is the fine structure constant. If it were a little bigger, then an atom wouldn't be able to stick together. And if there are no atoms, there could be no molecules, planets, stars, or life. Physicist Leonard Susskind highlighted this in his book, The Cosmic Landscape (page 175):
What if the fine structure constant were bigger, say about one? This would create several disasters, one of which would endanger the nucleus. Why is the fine structure constant small? No one knows. But if it were bigger, there would be no one to ask the question.
Many people say the constants are fine tuned just for life—but that’s not quite right. They’re fine tuned for everything amazing in the universe: from atoms to galaxies, and everything in between—including life. Of course, life is special, but it’s overstating the case to say that fine tuning is exclusively for life. (This is a really important point that answers many of the problems people have with the fine tuning argument.)
The Problem of Fine Tuning
The discovery of fine tuning caused a major problem for scientists. Saying we got incredibly lucky just wasn’t an option. It would be like randomly guessing a 25 trillion-digit password and getting it right on the first try. And remember those two explanations scientists had for the constants? Well, fine tuning shows that neither of them works at all. Here’s why:
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Saying “these constants are just brute facts” doesn’t explain why they’re perfectly tuned to result in a complex universe. It just remains a massive coincidence!
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Saying “maybe a deeper law set them” doesn’t explain how that law could hit all the right numbers by accident. It’s once again a huge coincidence with no explanation.
Fine tuning was definitely a great clue for solving the mystery of the constants, as it was the only genuine scientific knowledge ever discovered about these numbers. But what did it mean?
Fine Tuning Points to Intelligence
Let’s say you find a spaceship with 25 control knobs, and they’re all set exactly right to keep the ship running. Would you think that was just luck?
No way! You’d be sure someone intelligent set those dials on purpose.
That’s what fine tuning in the universe looks like. Out of all the possible values the constants could have had, they ended up being the exact ones needed for atoms, molecules, planets, stars, galaxies, and life. That indicates something intentionally chose them for the purpose of producing our complex universe.
That’s exactly what intelligence is—the ability to choose one setup out of many to reach a goal. So if the constants of nature were fine tuned to create our complex universe, it makes sense to say it was done by an intelligent cause—God.
Isn’t this God of the Gaps?
Some people might say, “Aren’t you just using God to explain something you don’t understand— a ‘God of the Gaps’ argument?”
But this isn’t about filling in gaps that we’re ignorant about. It’s about a real scientific discovery. We didn’t say, “We don’t know, so it must be God.” We said, “We do know—the constants are fine tuned—and that points to something intelligent.”
This isn’t an argument from ignorance—it’s an argument from knowledge.
Who Fine Tuned God?
Some people ask, “If the constants had to be fine tuned by God, doesn’t that mean someone else had to fine tune God?”
That’s a fair question—if we were saying that god is a complex being made up of many parts. Because if god were made of parts, then someone or something would have to fine tune those parts too.
That’s exactly why the fine tuning argument points to an absolutely simple intelligence behind the universe—something that doesn’t have parts and doesn’t need to be adjusted. A being like that wouldn’t be subject to the question “Who fine tuned God?” because it’s not made up of pieces that could be fine tuned in the first place.
The Multiverse: Scientists' Best Alternative
Fine tuning presented a major problem for scientists who assumed that God can’t possibly exist: How could they explain the precisely fine tuned constants without an intelligent cause?
The best explanation scientists could come up with is the multiverse—an infinite number of unobservable universes where everything possible happens. According to this theory, our universe is just one of infinitely many universes, each with different constants. Most of the universes wouldn’t have atoms, stars, or life—but we live in one of the rare universes that does.
You might wonder: What are the chances that we live in a universe with just the right conditions? The multiverse theory answers this by saying we had to end up in a universe like this—because life isn’t possible anywhere else. Out of all the possible universes, only the ones with fine tuned constants can support life. So while it feels like our universe is special, in truth it’s the only kind of universe we could ever live in.
While the multiverse might sound like science fiction or something out of a Marvel movie, it’s actually a serious theory that many scientists believe. Just the fact that scientists are saying something as wild as a multiverse shows that fine tuning is a big deal. But if you want to fully understand the fine tuning argument for God, you’ll need to dig a little deeper to see why the multiverse fails as a good scientific explanation.
