Here is a number I have thought about a great deal. Consider the energy contained in empty space — not the stars, not the matter, but the space in between, which it turns out is not quite empty. It has a value. And what is remarkable about that value is not how large it is, or how small, but how precise it has to be. If it were slightly larger, then after the beginning everything would have flown apart too quickly for a single galaxy, or a single star, ever to gather itself together; there would be only thinning gas. If it were slightly smaller, the whole universe would have collapsed back on itself before it began. The range of values that lets a universe hold together long enough to produce anything at all is, on the usual estimate, about one part in a number with a hundred and twenty zeroes after it.
I should say at once that this number is often used to intimidate people, and that is not what I am doing. But consider the shape of it, setting theology aside. Physicists often picture each constant of nature as a dial that could have been set to any value across an enormous range, where almost every setting yields a lifeless universe, and ours falls within the narrow band where stars ignite, carbon forms, and eventually something appears that can ask why the value is what it is. And it is not one constant but several — the strength of gravity, the energy of empty space, the forces that hold an atom together — and several of them fall within similarly narrow ranges. The impression this leaves, on believer and unbeliever alike, is hard to dismiss: the universe looks arranged. It looks aimed at something.
Whether that impression is telling us anything true is the whole of tonight's question.
This is Philosophy for Us. This is Is There Anyone There?, and it is the second of eight episodes. Last time we examined no argument about God at all. We did something prior: we went looking for the standard of proof each of us carries — the rule about what would count as evidence — and found that we deliver verdicts with it constantly and have never once read it back. No argument was graded and no winner declared; believer and unbeliever left with the same task. Tonight we turn to the first argument, the one many serious people regard as the single strongest case there is — the argument from the fine-tuning of the constants. And we take it up under the most demanding discipline I know, which I will set out before touching the argument itself, because the discipline is the real point and the argument is only where we practise it.
Here is the discipline, and it will feel backwards. Before one is allowed to object to an argument — before raising any difficulty, any "but surely" — one must be able to state that argument at its strongest. Not a weak version. Not one that is easy to refute. The version its ablest defender would hear and endorse: yes, that is exactly what I mean; you have understood me. Only then does one earn the right to object.
There is a name for this. It is called steelmanning, and it is the opposite of attacking a straw man. The straw man is the familiar cheat: one takes the opposing argument, builds a flimsy version of it, refutes the flimsy version, and feels one has won. Steelmanning refuses that. One builds the opposing case as strongly as it can be made — more strongly, perhaps, than its own defenders have made it — and objects only to that. The reason is not courtesy. It is that one learns nothing from defeating a weak version. The only version worth defeating is the one that might actually be right. If one cannot defeat that version, one has not earned one's position; one has merely flattered oneself.
So that is the rule for tonight, and where it falls hardest depends on where you stand. If you are the sceptic — if your immediate reaction is that the fine-tuning argument is plainly a dressed-up "god of the gaps," the kind of claim that retreats each time science explains another corner — then your task tonight is the hard one: to build the argument into something you cannot wave aside. The serious version is not the one in your head, and if you refute the one in your head you will have refuted a straw man and learned nothing. And if you are the believer, already leaning forward, expecting to be proved right — your turn is coming, and it is harder. In a later episode the strongest arguments will run the other way, at you, and you will have to build those to full strength before you may object. No one is permitted to be comfortable in this series. That is the arrangement.
And notice what this is not. I am not, tonight, going to judge between the arguments. Last time we went looking for the standard you would use to decide whether an argument is any good, and found you had never read it. I have not repaired that, and we are not judging tonight either. What I am doing is narrower and, I think, more useful. I will set the strongest version of this first argument beside its strongest critics, and I will not weigh in on either side. I will build the argument, build the case against it, and then stop — and observe what you do. Because something does happen to a person when an argument and its rebuttal both stand at full strength and no one has said who wins. We will come to what that is. For now, the argument itself.
Let me build the argument, and build it properly, because the version most people carry is the straw man — worth refuting, but not the argument.
The straw man runs like this: the universe is so beautiful, so finely arranged, that it must have been made. That is a feeling, not an argument, and a sceptic is right to be unmoved by it. A slightly better straw man is the "god of the gaps" version: science cannot explain why the constants have the values they do, and where science leaves a gap, God fits. That version deserves the contempt it receives, because it is a losing wager — science closes gaps century by century, and a God who lives only in the gaps grows smaller each year. If that were the fine-tuning argument, we could stop here. It is not.
Here is the real one. Its ablest living defender is Robin Collins, a philosopher and physicist, and his version mentions neither beauty nor gaps. It is a comparison — the ordinary kind one makes many times a day. Set two pictures of reality side by side. In the first, there is a single universe, and the constants took their values for no reason at all — brute luck, the way a tossed coin comes up heads. In the second, there is a mind of some kind behind it, and that mind has at least some reason to want a universe in which conscious life could eventually exist. One need not believe either picture. Simply hold both. Now consider the one fact we are most sure of: this universe permits life; it contains us. And ask the only question that matters: under which of the two pictures was that fact more to be expected?
Under the first, a life-permitting universe is one almost unimaginably fortunate setting among a vast range of lifeless ones — one part in a number with a hundred and twenty zeroes after it, and that is only one of the constants. Staggeringly unlikely. Under the second, a life-permitting universe is more or less what one would expect; it is the sort of thing a mind that valued life would aim at. And there is a rule of reasoning, an entirely ordinary one: when a fact is very unlikely under one explanation and unsurprising under another, that fact is evidence for the second. Not proof. Evidence.
Notice how modest and how precise the argument is at once. Collins is not saying, "you cannot explain the constants, therefore God." He is saying: suppose physics one day explains exactly why the constants sit where they do — that would not touch this, because the question was never whether we can explain it, but which picture of reality the fact is at home in. Nor is he asking for awe. He is asking for a piece of reasoning one already trusts. Suppose you reeled in a fishing line and found it had hooked, on the first cast, the single tagged fish in a lake of millions. "How lucky" is available to you — but "someone placed it there" is the better inference, and you know it is, and you would act on it. Collins is saying the universe is that fish.
This is the argument the sceptic has to answer — not wave aside, and not meet with "god of the gaps," which I have removed from the table. The serious fine-tuning argument is a clean likelihood comparison made by careful people, and it has genuine force; a reply that amounts only to dismissal has not met it, but only the straw man. So before objecting — and there are objections, strong ones, and they are close at hand — be sure you can state it as Collins would wish it stated. The constants are real. The narrowness is real. And "it points to something" is not a foolish conclusion for a thoughtful person to reach. Hold all of that. Now let us see whether it survives the objections.
So the constants are before us, set to that extraordinary precision, and the argument says: this points to something. Now the critics arrive, and I will give them their full weight as well, because that is the arrangement — and they are not cranks. They are the reason this remains a live dispute in 2026 rather than a settled one.
The first and largest is the multiverse. The fine-tuning argument rested on a single word: one universe, the constants set once, by luck. But suppose ours is not the only universe. Suppose there is a vast ensemble of universes — countless, perhaps endless — each with its constants set differently, most of them lifeless, a scattered few alive. Then a life-permitting universe is no longer a near-miracle but a near-certainty somewhere, in the way that buying every ticket guarantees a winning one. And here is the sharp point: the only universes that can contain anyone to notice how finely tuned things are, are the ones tuned finely enough to produce such observers. So of course we find ourselves in a life-permitting one; we could find ourselves nowhere else. The dice were not loaded; there were simply an unthinkable number of throws, and we occupy a winning throw because the losing throws have no one to occupy them. And this is not a desperate device invented to avoid God: serious cosmology reaches for multiverses for its own reasons, out of inflation and out of string theory. It is a real idea with real physics behind it.
That is the largest objection. Beneath it sits a quieter one, just as important, sometimes called observation-selection. It is the point I introduced a moment ago: we could only ever find ourselves in a universe that permits us. So, the critic says, "the universe permits life" cannot really be surprising to anyone in a position to be surprised by it, and a fact that cannot surprise cannot be evidence for anything. But watch Collins answer this, because the reply is a good one. Suppose you are placed before a wall, a hundred trained marksmen take aim, the order is given, the guns fire — and you are still standing. Every one of them missed. It is true that you could only ever notice that you had survived; a dead man notices nothing. But would you really shrug and say, "no surprise there, I could hardly observe otherwise"? You would not. You would think: someone arranged this. That survival was the precondition of your noticing does not make the survival unremarkable. So observation-selection does not dissolve the argument cleanly; the astonishment survives the logical point. And the critic has a reply to that reply, and so it continues — which is precisely the point.
And then the deepest objection, which does not dispute the answer but questions the question. The whole move — one part in a number with a hundred and twenty zeroes after it, therefore wildly improbable — assumes that probability can be spread evenly across the range of values the constant could have taken. But what if that range is infinite? Then there may be no coherent way to say what is probable and what is not, because a finite amount of expectation cannot be spread evenly over an endless line; the usual probability rules do not apply. And if the probability cannot even be well defined, then "fantastically improbable" is not a bold claim but a confused one, and the argument never gets started. This objection is technical, and it challenges a basic assumption of the argument, and the argument's defenders know it and are at work on it. It does not refute the argument. It leaves the argument's key probability undefined, exactly where it needs a clear number.
So — what is one to do with this? Three serious replies, each met by a serious counter-reply. The multiverse explains the tuning, but no one has observed another universe, and it merely relocates the luck: why should there be an ensemble-making mechanism that itself happens to produce life? Observation-selection looks decisive until the firing squad makes one doubt it. The probability worry is real but unsettled. There is a published exchange between Collins and a sharp atheist philosopher, Peter Millican, in which two careful people work at exactly this, at length, in good faith — and do not resolve it. They leave the table with the matter still standing between them. That is not a failure of the conversation. It is the actual state of the question. And I am not going to pretend to a resolution they could not reach. I will not tell you whether the constants point to something or are simply where we happened to find ourselves. Both readings entered as strongly as they can be made, and both remain standing.
Before you go, let me point to something you did in the past half hour, without telling you what it means — because what it means belongs to a later episode. Tonight, simply catch yourself doing it.
You were keeping score. I would wager on it. As I built the fine-tuning argument, part of you was judging each step — "good point," or "that is a stretch." When the multiverse arrived, you weighed it — as a relief, perhaps, a clean way out; or as a cheat, an idea invented to make one awkward fact disappear. When the firing squad appeared, you felt the argument pull back the other way. The whole time, point by point, you were adding things up, running a quiet tally of everything I said. That is not a criticism. It is simply what a mind does with an argument, and it is worth catching, because we will return to it, and it will matter more than anything I said about cosmology. For now, only note that a tally was running at all, the entire time, and leave it there. Do not go looking at it yet.
Here is the thing to take and use, because an argument you have only watched is not yet yours; you have to run it with no one setting it up for you. Choose the side you lean against. If the constants left you cold — if your instinct is "luck, plainly" — then your task before next time is to build the fine-tuning argument, the Collins version, the likelihood one, not the straw man, until you could state it to a believer and have them say: yes, that is it. And if the constants left you certain there is a hand behind them, then build the multiverse, until it stops being a dodge and becomes the serious idea it is. Build the side you do not hold until its ablest defender would accept your statement of it. Only then object. You will find two things happen. The objecting grows harder. And the certainty you walked in with grows quieter. That quiet is the whole of the exercise.
Next time, the arguments run the other way. We have spent tonight on the strongest case for; next time it is the strongest case against, and it comes on two fronts, both of them the ones a believer would rather not face. First, suffering — not suffering in general, but the particular horror that appears to be for nothing at all: a fawn, somewhere, burning to death in a forest fire no human will ever see or learn from, days of agony serving no one and teaching nothing. And second, silence — the place where a love that genuinely wished to be known would surely have said something, anything, and where honest people who go looking with open hands find no one there. Two arguments, built properly, each with its strongest answer beside it. And — you can see the shape of it by now — neither settled when we are done. The same discipline, a harder exercise, the other direction.
So — is there anyone there? Tonight the constants lie before us, set to a precision it is hard even to state, and I have not moved you an inch. Perhaps that narrow range is a sign that something leaned in and aimed a universe at us. Or perhaps it is simply the one place where an observer could ever wake to wonder about its place, in a cosmos vast enough, or plural enough, that somewhere had to come up alive. I have not told you which. I genuinely will not. Both remain standing as we close — and the only thing different from an hour ago is that you have now met the strongest version of each, rather than the straw man, and you can feel how much harder it is to be sure once the straw man is gone.
Thanks for listening. I'll see you next time.