The fine-tuning argument is an argument from design or purpose (aka teleological) just like biological irreducible complexity is.
If I was rating arguments for God in previous years I would have initially put this argument at the top of the list, but after doing some more research it has fallen way low on the list and has even fallen below irreducible complexity (which is already low due to the fact that consensus among experts in the relevant fields of study is that irreducible complexity has no basis scientifically.) It turns out the fine-tuning argument suffers from way more than just the possibility of the multiverse, and I was surprised to find out that some of the most coherent arguments against it are explained by evangelical Christians, and most skeptics are not even aware of those arguments.
First the facts: there are several constants in the equations of physics that if modified by very small amounts would cause a universe that would be dramatically different from our own. The claim is that those universes would not be life permitting, but there are some who contend that this second claim is not actually a proven fact. If you want the details for the positive claims you can hear them very clearly in practically any debate on God with William Lane Craig in it.
Do We Know The Probabilities?
The first and probably the toughest issue for fine-tuning is explained very well by mathematician William Dembski (a Christian apologist who believes design can be found in biological irreducible complexity):
In layman’s terms, the issue is that even though the constants might sit within a tight range we have no way of figuring out what the probability distribution of those constants are because we don’t have empirical access to universe generators. As a result we have no way of finding out what the probability is of the constants being in that tight range. For all we know the probability that they sit in the range they do could be high. Without access to universe generators we cannot know. The discussion with Dembski goes longer and he explains himself more – you can see it here.
This along with other probability issues are explained in mathematical terms in this paper by Timothy McGrew, Lydia McGrew, and Eric Vestrup, all of whom are Christian apologists. Eric Vestrup is a mathematician and the McGrews are epistemology philosophers. It gets a little technical but overall it’s not too bad, and if you truly want to understand the issues involved with fine-tuning you need to understand their paper. Lydia McGrew explained some (not all) of the issues described in the paper starting at time “51:00” in this interview with Luke Muelhauser. Here is a very short clip of Lydia expressing her misgivings about the concession:
A short summary of the paper in my own words:
– Page 203: If we assume a uniform probability distribution, since the range of values for the constants are infinite, no matter how we break them up into pieces the sum will always be infinite. However, for probabilities to make sense the sum of all possible alternatives must add to 1 (i.e. 100%). This is called the “normalizability” problem, and it means we have no way of assigning probabilities to the range of the constants.
– Page 205, paragraph 2: The above assumes a uniform distribution, so to get around it we can assign a different kind of probability distribution. But what distribution do we pick? This is exactly the problem that Dembski described. There is currently no valid way to know what to pick.
– Page 206, paragraph 1: Here they allude to important questions related to fine tuning that I have always wondered about. How do we know that there cannot be other constants or forces in possible universes? Put another way, we are so fixated on varying the constants that are in the equations we’ve found, but what about varying the equations themselves? What is the evidence that causes us to think that the constants can be changed while the equations cannot? It seems like the only reason for this very well may be psychological – the constants seem to be the easiest thing for our brains to ponder varying. In summary, given this infinite possibility of varying equations, “we may not be in any position to speak of the life-friendliness of universes”.
– Page 207: They essentially say what Dembski said.
This direct quote from the article summarizes things well: “The point of the argument was supposed to be that objective results in modern cosmology virtually compel disbelief in a chance origin of the Universe. If, at a critical point, the argument turns on a subjectively variable sense of which assessments of probabilities are reasonable, a sense that cannot be adjudicated in terms of any more fundamental criteria, then the FTA is effectively forceless. To retreat to the point where the argument rests on unargued intuitions is to deprive it of anything more than devotional significance.”
An Enlightening Debate
This debate between William Lane Craig and Sean Carroll was very educational:
Craig gives his pitch for fine-tuning starting at 38:48, and Carroll gives his response at 54:17. It comes up several other times in the debate (at 1:12:12, 1:21:47, 1:42:31, and 2:35:28). Here are some issues that Carroll brings up:
– The conditions under which life can exist, and what life is, have not been clearly defined enough to prove the fine-tuning argument. While our human form of life may not be common after varying parameters, some kind of conscious minds could exist in many other different universes. While he may very well have a point I believe he is currently in the minority on this point, perhaps because varying some of the parameters often results in very short-lived universes not allowing for complex beings to arise. I’m not sure about this one, but I think it’s at least valid to question how thoroughly this has been defined.
– The next objection is a bit more philosophical in nature and while I find it a bit confusing to think through it may very well be a valid objection. Carroll says: “in theism life is not purely physical, it’s not purely a collection of atoms doing things like it is in naturalism. I would think that no matter what the atoms were doing God could still create life. God doesn’t care what the mass of the electron is, He can do what he wants.” (please don’t say something silly like “I thought Sean didn’t believe in God, but now he is talking about Him”). This is an interesting conundrum for the fine tuning argument itself. Theism posits a certain view of God, but then the argument doesn’t seem consistent with that view. Sean’s final statement here may also shed some light on this: “the only framework in which you can honestly say that the physical parameters of the universe must take on certain values in order for life to exist is naturalism.” I’d like to add here that Lydia McGrew also mentions this as an issue in her interview with Luke Muelhauser (above), and apologist Hans Halvorson (see link below) concedes it as well in his debate with Carroll.
– The third objection is more technical and I believe is a valid one: the “apparent” fine-tuning of some constants actually disappear on closer inspection. The example Carroll gives is the common example of the early expansion rate of the universe. Claimed to be fine-tuned to 1 part in 1060. But after doing a correct, rigorous derivation of the probability using the equations of general relativity you find that the probability is 1. You can read further on this example here. Craig used to use this example in his debates and took Hawking’s statements out of context. To be fair he has corrected himself and no longer does that. It’s important to keep in mind the following statement from Carroll to get some balance to this objection: “I can’t say that all parameters fit into that paradigm, but until we know the answer we can’t claim that they’re definitely fine-tuned.” The debate over this objection that I’ve seen usually lies in questioning that last sentence of Carroll’s – the claim is that many cosmologists have thrown their hands up at this point and given up on getting answers that explain the apparent fine-tuning of many of the constants. A lot of cosmologists do seem to indicate this but I’ve seen some interviewed who have not given up. Either way though one could argue that this is still a God of the gaps argument because as we’ve seen many times in the past, not having answers to tough problems does not mean they are unsolvable with naturalistic explanations.
– 4th is the most common explanation among naturalists – the multiverse. I think this is a perfectly valid objection to fine-tuning and none of the responses to it have moved me. The idea is that there are many universes out there with many different constants and we just happen to be living in one of them. The perfect analogy is that we used to think the conditions of our planet were finely tuned for life to exist, but once we became aware that there are tons of planets in the universe this conundrum was gone. This is known as an “observer selection effect”. Craig’s response is that universes with boltzmann brains are more likely than universes with embodied living beings, so he claims that means the observer selection effect is nullified. But it is still agreed that with a multiverse there could be universes that have embodied living beings, and so the selection effect is still valid – we happen to be in one of those universes. Just because there are lots of other universes with other types of observers doesn’t nullify that. Also, Craig seems to misrepresent the hypothesis by saying “in order to rescue the alternative of chance it’s proponents have therefore been forced to adopt the hypothesis that there exists a … multiverse” (40:47), and then “now comes the key move” – as if it’s some sort of tactic. My understanding is that the multiverse is actually a prediction of physical theories (mainly inflation). And as I’ve seen written by some cosmologists, this is “indirect” evidence for the multiverse. The hypothesis is not created as a “rescue” for an objection to fine-tuning. And frankly even if it was I don’t see why that would really be an issue anyway. This could be a valid hypothesis on it’s own. Where is the need to add ideas of supernatural when cosmologists have never had any confirmed empirical evidence for that? Carroll responds to other objections to the multiverse here.
– His last objection is that even if we grant that the constants are fine-tuned theism is a poor explanation. I’ve gone way too long, so you can watch at (59:38).
Links to More Objections
– Hans Halvorson (Christian apologist) explains why he agrees with Carroll that the fine-tuning argument is not convincing – at time 28:41 in their debate. It’s worth a listen.
– While inconclusive, Don Page (an evangelical Christian) has a paper explaining that different values of the cosmological constant would have produced universes which were way more life permitting than the one we are in. It is at least another hint at the fact that the constants may not be tuned for life.
– Keith Parsons describes a good philosophical point that comes up a lot. It is the same objection that I have to the Cosmological Argument (mentioned here) and I haven’t figured out a good reason why the objection does not make sense.
– This is a link to a long list of objections to fine-tuning which is worth looking over. It is important to note that the strength of these objections span the map and several of them are very poor.
Links in Support of Fine Tuning
Luke Barnes (agnostic who who seems to lean toward theism) is one of the better expositors for fine-tuning. You can also listen to an interview he had with Luke Muehlhauser here.
Robbin Collins is another educated proponent for fine-tuning. His form of the argument is more polished than William Lane Craig’s but it’s also a weaker form of the argument.
I give more links in support as well as criticism of the argument on my companion page.
Summary
Given all of the issues, some of the strongest of which are even brought forth by theists, the fine-tuning argument does not look to me like a very convincing argument. And it surely cannot be claimed that those skeptical of it are doing so only because they don’t want to believe in God. While I would never say that everyone should give up trying to find out if this argument can really fly (certainly further research and study could possibly resolve objections), it seems to me that this one is a bit of a dead-end. On my companion page to fine-tuning I give references both for and against the argument so people can research further to try to form their own conclusions.
Truth Is Elusive 