1. The FT Argument
Back to philosophy of religion. Caveat: as I see it, the Fine Tuning Argument is an argument for intelligent design (ID), rather than theism. What’s the difference? ID says that some intelligent being created the universe, or the laws of nature, or at least adjusted very large aspects of the universe and/or the laws. That being may or may not qualify as a “god”. So don’t complain that the FTA doesn’t establish some godlike property or other.
The argument, in brief: there are certain very broad, fundamental features of the universe that I’ll call the “parameters” of the universe. Example: the gravitational constant; the mass of a proton; the ratio of electromagnetic to gravitational force; the initial entropy of the universe. It happens that many of these parameters have values in an extremely narrow range of values that would make it possible for life to exist.
Example: they say that if the gravitational constant were just a little stronger, then the universe would have re-collapsed shortly after the Big Bang, long before there was enough time for life to evolve. If it was a little weaker, the universe would have expanded too fast for planets to ever form, so again there would be no life.
There are other things like that that have to do with chemistry, where if some parameter were changed a little bit, then there wouldn’t be any elements heavier than hydrogen, or something like that. I forget the details.
The biggest example: Entropy. In our experience, entropy is constantly increasing, heading toward thermal equilibrium. After the universe reaches thermal equilibrium, life will be impossible, as will everything that's interesting. Given the probability distribution standardly used in thermodynamics, the state of thermal equilibrium is by far the most probable state (it occupies nearly 100% of the phase space).
Now, according to orthodox cosmology, the universe began about 14 billion years ago with the Big Bang. What caused the Big Bang? Unknown; maybe nothing. According to the traditional Big Bang theory, the time of the Big Bang was the first moment of time, so nothing caused it. It just was like that. The first thing that ever happened was that a huge amount of mass/energy was in a tiny space, moving outward.
That already seems pretty crazy. But now, if a universe was going to just start, for no reason, in some initial state, then I guess it could equally well start in any physically possible state. (I mean, if it’s possible for a universe to start for no reason.) Then the probability is overwhelming that, if a universe appears for no reason, it should appear in thermal equilibrium. Roger Penrose has calculated that the probability of the initial state being what we actually take it to have been is on the order of 1 in 10^10^124. (That’s ten to the power of ten to the power of 124.)
The incredibly low-entropy initial state of the universe is what is driving all interesting processes that we care about, including life. You need a certain amount of initial order (in the thermodynamic sense), and life sustains itself by using up that order, so to speak, expelling entropy into the environment.
It looks to me like we need an explanation for all this. Why does the universe have parameters that allow for life to exist?
Possible explanation: ID. The Intelligent Designer intentionally adjusted the parameters to make life possible. Maybe this is the best explanation (can you think of a better answer?). That’s a reason to believe in ID.
2. Bad Objections
When the FTA comes up, suddenly atheists start raising objections that sound like the sort of unfalsifiable dodges you usually associate with theists (if you’re a theist, or an atheist, sorry. But that’s how it seems to me.) – we get objections that are so skeptical that they would pretty much reject any theory, we get totally implausible speculations, and we get simple misunderstandings of the argument.
2.1. First bad objection: The anthropic principle
There’s supposed to be a profound principle called “the Anthropic Principle”. I have a hard time figuring out what people are talking about when they invoke this, though. (I read some literature on it, and it didn’t help much.) Usually, the AP is explained with some trivial tautology, like: “Conscious beings can only exist in conditions that allow for conscious beings to exist” or “Living things can only find themselves in universes that permit life.”
Yeah, of course. But then people seem to think that the AP somehow answers our question, or renders the question moot or inappropriate, or something. I really don’t get it, so maybe someone will show up and explain it to me. It seems like people who try to respond to the FT Argument by invoking the Anthropic Principle are thinking something like this:
“We could not exist in a universe that didn’t allow for life. So that explains why this universe allows for life.”
Or:
“We could not exist in a universe that didn’t allow for life. So we don’t need any explanation for why the universe allows for life.”
Those are both bad inferences. Example (I think this comes from John Leslie):
The Firing Squad: You’re supposed to be executed by a firing squad. The soldiers take aim, fire, and . . . somehow you survive. Every single shooter must have somehow missed. That’s super-improbable, so you start wondering, “Why did they not kill me just now?” You start to hypothesize that maybe someone paid off all the shooters to spare you, or got into the armory last night and put blanks in all the rifles, etc.
Now imagine some helpful philosopher shows up and tells you (as you stand there waiting for the shooters to reload): “Oh no, there’s no reason at all to entertain any theory like that. You see, there’s this thing called the Anthropic Principle, which says that you can only find yourself living at a time when you haven’t been killed. So, that explains why the shooters missed.”
Or: “You can only find yourself living at a time when you haven’t been killed. So you don’t need any explanation for why you weren’t killed.”
No, false. Granted, the AP is (trivially) true. But it doesn’t explain why you weren’t killed, and it doesn’t show that you don’t need any explanation. No one would make either of those mistakes, except when the topic of a creator of the universe comes up.
2.2. Who knows what a universe-designer would want?
Objection: “Sure, we think life is great because we’re alive. But if there’s a universe-creator, it’s a totally different kind of being from us, so how can we know what it would want? Maybe it would want a universe filled with nothing but hydrogen. Why assume it would want there to be life?”
I think this is so completely implausible that it makes me feel like I’m being trolled when people say this. Or maybe the objector just doesn’t get how probabilistic arguments work. Let’s assume that.
The FTA is a probabilistic argument (specifically, an inference to the best explanation, which is always probabilistic), not deductive. We’re not saying that it logically follows from fine tuning that there’s an ID’er. We’re also not saying that it logically follows from the existence of an ID’er that there would be life.
For evidence E to support hypothesis H, what is necessary is this: P(E|H) > P(E|~H). In this case: the probability of a life-permitting universe given an intelligent designer is greater than the probability of a life-permitting universe given no designer. And that probabilistic relation, I think, is just obviously correct. I’m not claiming to have detailed, deep understanding of the thoughts and motives of the intelligent designer if there is one. But there are many interesting things that can happen, and many comprehensible values that can be realized, in a universe with enough order to have life, which can’t be realized in a universe with nothing but hydrogen atoms spreading through space forever. So no, it is not equally plausible that an intelligent designer would want the hydrogen-only universe.
By the way, if you agree that there is at least a 1 in a trillion chance that an ID'er would value life, that's enough for the FT Argument to work. (1/10^12 is huge compared to things like 1/10^10^124, etc.)
2.3. The universe does not maximize life
Objection: “If there’s an intelligent designer, and it values life, then the universe should be filled with life. But there is only a tiny amount of life, compared to all the non-living matter (and empty space).”
Reply: It’s hard to say how much life there would be, not knowing what the ID’er’s capabilities, beliefs, and desires are. Perhaps it was unable to create a universe filled with life. Perhaps it wanted life from different planets to be far away from each other. Who knows? Granted, it’s perhaps more likely that there would be a lot of life rather than a little, if there’s an ID’er. But it’s far from certain. Meanwhile, it’s still vastly more likely that there would be some life given an ID’er than given no designer, for the reasons given in section 1.
2.4. Different kinds of life
Sometimes people say,
“How do you know there wouldn’t be life if the parameters of the universe were different? Maybe there would just be a completely different kind of life, with different requirements?”
Again, totally implausible, if you’re following what the FTA actually says. The FTA doesn’t rely on some highly specific facts about the human body or other Earth-bound organisms. It relies on extremely general requirements for life. E.g., if there were no stars, or if the universe had re-collapsed before planets formed, or there were no elements heavier than hydrogen, then no, there obviously would not still be life.
To help gauge plausibility, imagine someone making parallel claims about conditions in our actual universe: imagine someone claiming that maybe there is life on the sun – it’s just a “different kind of life” from the life we’re familiar with on Earth. Or maybe there’s life in interstellar space, made out of the few stray hydrogen atoms floating there. Or maybe there is life in a black hole.
No, there isn’t, and no one would seriously entertain such hypotheses in a normal context – that is, if they weren’t trying to avoid an argument that might upset their worldview.
(Most people are afraid of having their current worldview upset. I’m not. I just want to figure things out; I don’t care if it’s what I initially thought or something completely different. I recommend this attitude to you.)
2.5. We can’t assign initial probabilities
Objection: “There is no good theory about how to assign prior probabilities to things, prior to obtaining evidence. So we just can’t say anything at all about the probability of the universe having life-permitting parameters. We can’t say whether it’s probable or improbable that they would fall in these incredibly tiny ranges that permit life to exist. And thus we can't make any probabilistic inferences about this.”
I think this is an example of people being so afraid of an argument for ID (which they probably confuse with theism, which they might in turn confuse with Christianity) that they’re ready to throw out everything else and embrace radical skepticism. If this objection undermines the FTA, it does so because it undermines all probabilistic reasoning. Which means it undermines basically your entire belief system – outside of the stuff you’re presently observing right now. (Here, look at this paper: http://philpapers.org/archive/HUETIN.pdf.)
Anyway, here’s an analogy. Imagine that we discovered that there was a law of nature, or perhaps a collection of laws, with this consequence: whenever there is a large enough sample of iron, the atoms spontaneously arrange themselves into crystals at the microscopic level, and these crystals just happen to have the exact shape of the English words “Made by God”. Just pretend that we had discovered that. For good measure, add the following: astronomers searching the night sky discovered a constellation, visible with telescopes, in which the stars also spell out the English words, “Made by God”. And this isn’t one of those lame constellations that you need a lot of imagination to see; this one looks exactly like that sequence of words, to everyone who looks through the telescopes.
Now, the above objection implies that this wouldn’t be any evidence for anything at all. We should just shrug our shoulders and say, “Well, the iron atoms and the stars had to be arranged in some pattern. Why not that one? Who says that that’s improbable? After all, there’s no way of assigning prior probabilities.”
3. The Multiverse Theory
I think there is one good alternative to the FTA. It’s the multiverse hypothesis: there may be a large number, perhaps an infinite number, of parallel universes with different parameter values. The more of them there are, the higher is the probability that there would be some life-permitting ones. So this is a possible explanation for why there is a life-permitting universe.
Of course, there would also be a much larger number of non-life-permitting universes, but we wouldn’t expect to see any of those even if they exist, so we can’t take that as evidence against the multiverse theory.
The “this universe” objection
Suppose you flip a coin and it comes up heads 10 times in a row. Q: Does this provide evidence that many other people are flipping other coins, somewhere else?
Obviously not. But that inference seems kind of like the multiverse inference.
Here’s the problem: The probability of getting 10 heads in 10 flips is 1/1024. Now, if there are many other coin-flippers, then the probability that at least one of the coins comes up heads 10 times goes up. However, the probability that this coin (the one you’re looking at) would have come up heads remains 1/1024; it is completely unaffected by the other coins. So, if you get confused and think that your evidence is “Some coin came up heads 10 times in a row”, you could conclude that you have evidence for other coins being flipped. But your evidence isn’t “Some coin came up heads 10 times”. Your evidence is “This coin came up heads 10 times”. The hypothesis of other coins is completely irrelevant to that.
Similarly, if our evidence is, “Some universe contains life”, then that supports that there are many universes. But if your evidence is, instead, “This universe contains life”, then the hypothesis of other universes is completely irrelevant to that. You don’t have evidence for other universes, any more than you would have evidence for other coins in the above example.
That is the “this universe objection”. I used to think it was decisive, because I thought our evidence is clearly that this universe has life-permitting parameters. But now I think there is a plausible response, but it’s a response that hardly any anti-ID people would like. Suppose that you are not necessarily bound to this universe but instead could exist (i.e., would have some chance of existing) in any life-permitting universe that existed. In that case, I think the multiverse explanation works. It would indeed be more likely that you would have the evidence you have given that there’s a multiverse than given only 1 universe, because the more universes there are, the greater would be your likelihood of finding yourself alive in some universe.
On the other hand, I think that if persons are necessarily tied to the particular universe they are in (you could not have existed in any other universe, even if there were other ones), then I think your evidence is indeed completely irrelevant to the multiverse hypothesis (i.e., the evidence neither supports nor undermines the hypothesis).
Most anti-ID people, however, would probably say that persons are essentially tied to the particular universe they are actually in. That’s because they’d say that persons are just particular physical objects, and a particular physical object couldn’t have existed in another universe (or so I assume).
Conclusion
Maybe there was an intelligent designer, or maybe there is an infinite multiverse and individual persons are able to be incarnated in any of the universes that contain intelligent life.
These are both fairly amazing ideas, and amazing ideas are usually false. But the alternative of fine tuning happening with no explanation at all is much more incredible.
Re: AP principle probabilistic explanation
Let A be "There is at least one concious being that's able to question why they exist and why the parameters of the universe are such that allow them to exist"
Let B be the distribution of possible parameters of the universe (if you believe there is any) (including ID existence or not existence as a parameter not independent to all others parameters, I suppose)
Let C be "Parameters of the universe are such that allow conscious beings to exist"
Let D be "ID exists"
Several possible explanations why ap is correct:
First and foremost the question of "why parameters are such as we observe them if the P(A) over B is really small" is a bit of begging the question.
1) If you really believe in the paradigm "Universe parameters are taken out of some distribution which splits by random variable D", your priors shouldn't be updated at all if you observe yourself in the state A, since -> P(C|A) = 1, since A is (C & conscious beings exist) and A is clearly true (you exist).
So now for you to claim that ID exists is to claim that prior to your experience of the universe P(C) over (B|~D) is lower than P(C) over (B|D), which is a meaningless question since there is no way you could've observed the universe prior to observing one.
So, the question of whether ID exists is actually the question not of comparing P(C|(B&D)) with P(C|(B&~D)) but of comparing P(D) with P(~D) , which makes this question straightforwardly meaningless. In other words P(D|(C&A)) over (B|A) vs P(~D|C&A) over (B|A) is actually equal to P(D) vs P(~D).
Not sure I was able to phrase it correctly but it seems like this post is the case about wrong Bayes reasoning being done if you assume that you have some knowledge about universe prior to actually being in that universe.
2) I have to say that you don't actually know whether the distribution from which parameters are taken exists at all, and what the process looks like. I.E it's sorta weird to assume that before this universe was created infinitely-many parameters were taken out of some distribution of UNIVERSE parameters and afterwards the universe was initiated with them taking place. It seems to me like it's just an obscure question since we don't know anything at all about universe parameters distributions. (we only observe one universe).