The fine tuning argument is in principle quite simple. Atheism strongly predicts that this universe will forbid life. Theism strongly predicts that this universe will permit life. Clearly, the universe does permit life, so this favours theism over atheism.
Let’s elaborate on what it means for the universe to permit life. I’m not referring to things like the location of Earth relative to the Sun (though others have done so), instead I’m talking about universal constants. Things like the charge on an electron, or the gravitational constant, or the rate of the expansion of the universe at the Big Bang. It’s no secret that these constants are finely tuned to create a universe that can permit life, and if they were changed often by a fraction of a percent, the universe itself could not exist for more than a few seconds. Sometimes not even that.
In support of this, I’ll cite some physicists:
- Stephen Hawking:
“The remarkable fact is that the values of these numbers seem to have been very finely adjusted to make possible the development of life… It seems clear that there are relatively few ranges of values for the numbers that would allow the development of any form of intelligent life. Most sets of values would give rise to universes that, although they might be very beautiful, would contain no one able to wonder at their beauty”
- Paul Davies (British astrophysicist):
“There is for me powerful evidence that there is something going on behind it all….It seems as though somebody has fine-tuned nature’s numbers to make the Universe….The impression of design is overwhelming”
- Arno Penzias (Nobel prize in physics):
“Astronomy leads us to a unique event, a universe which was created out of nothing, one with the very delicate balance needed to provide exactly the conditions required to permit life, and one which has an underlying (one might say ‘supernatural’) plan.”
I’ll allow you to do your own research on the topic, but the fact is that the level of precision in the cosmological constants is overwhelming. This paper gives some more details about the specific constants.
Many people will counter this argument by appealing to the anthropic principle. That is, the fact that we are observing the only type of universe that could permit us is not surprising, because we are here to observe it. We could not observe it if we did not exist.
It’s clear that this type of reasoning alone is not sufficient. Anthropic reasoning only indicates that the probability that the universe will permit life given that it is observed is high. It doesn’t indicate that the probability that the universe will permit life given atheism is high. If I were about to be executed by a firing squad of 100, I heard them all shoot, and then observed that I was uninjured, I’d rightly be surprised. It’s true that it’s not surprising that I’m observing it, given that I’d have to be alive to observe it. But it is surprising that all 100 missed. That’s the flaw in this reasoning.
Another common counter-argument is that the cosmological constants can’t actually vary. That they must necessarily be the way that they are. That the laws of physics couldn’t have been different, and neither could the starting conditions of the universe. It seems to me that if you’re willing to accept this, then you implicitly accept the Principle of Sufficient Reason, which states “For every true fact, there is a reason or explanation for why that fact is true”. To accept that the physical state of the universe is necessary is to accept the PSR for at least the physical universe.
If you’re happy to do that, then you should stop reading this argument and instead read my page on the cosmological argument, since the PSR is one of the premises of that argument. If you reject the PSR, then you only have one option available to you to reject the teleological argument.
By far, the most common objection to the teleological argument is the argument that there exists some large (perhaps infinite) number of universes. Couple this with the anthropic principle mentioned above, and you do seem to have a strong objection to the argument.
So why should we reject the multiverse? The most obvious argument is that of Occam’s Razor. We shouldn’t multiply entities needlessly. Since we’re talking about something on the order of 10^500 universes (there are 10^80 atoms in the observable universe) that’s a huge multiplication of entities. Entities that we can not observe, and have no evidence for. If our options are either a designer of this universe, or an unimaginably large number of universes, one of these certainly seems to have fewer entities.
Let’s suppose, however, that we don’t accept Occam’s Razor. We might have good reason to reject it here: under a model like Vilenkin’s, it’s not clear that the universes in the multiverse are separate entities, they are just different locations in space. Or perhaps we take a different understanding of Occam’s Razor, perhaps it is not entities that we want to avoid multiplying, but types of entities, or perhaps behaviours.
Let’s suppose that there is some huge number of universes. Then there must be something which has conditions which allow multiple universes to begin. Vilenkin proposes such a meta-universe, but this structure itself requires some fine-tuned constants in order to exist. Vilenkin requires a particular level of inflation for his model, for example. We have not really defeated the argument, instead, we’ve just moved the problem.
(The existence of a multiverse comprising mostly life-forbidding universes would lower the degree to which theism predicts that this universe will permit life, but multiverse-hypotheses only predict a generally life-forbidding multiverse given atheism, which begs the question in this context.)
I am no physicist, but the interpretation of QM which predicts multiple universes is not popular among physicsts who specialize in foundations of quantum mechanics, instead the most popular interpretation among this group is a pilot wave theory, in which not only is there no multiverse, but the universe is in fact deterministic. So even appealing to physics doesn’t necessarily make the case for a multiverse.
For a more detailed discussion of more modern inlfation multiverse models, see chapter 5 of this paper. I will in the future attempt to produce a summary of this, but for now the paper will have to do. Helpfully, the author of the paper also wrote this blog post in summary.