A popular argument used these days by those who seek to prove the existence of God is that a handful of key numbers that calibrate the laws of physics appear to be very ‘finely tuned’, as if a designer had specifically chosen the values that they have. ‘Finely tuned’ here means that if the numbers were significantly different, the universe would have been too chaotic for complex structures, intelligent life in particular, to evolve. The suggestion is that this is evidence that the numbers were chosen by some intelligent designer, ie God.
This argument may carry weight with some and if it makes them more secure and happy in their theistic beliefs I wish them much joy from it, as long as they don’t attempt to impose their beliefs on anybody else. But in my mind, far from providing the knockout blow some believe it possesses, it gains no traction at all. Such an observation is principally an observation of how one feels. Sometimes a new idea comes along that makes us think “oh… there could be something in that”, which leads to a questioning of our existing ideas and in some cases a revision of our beliefs. It’s the feeling that starts the process, and the rational inquiry occasioned by the feeling that completes it. But in this case I felt nothing at all, not even surprise about the ‘fine tuning’. Why?
I decided to think about this, given that some people find these constants such a compelling argument, and after a period of reflection, concluded that the ‘fine tuning’ just didn’t seem remarkable to me at all, for three principal reasons, which I discuss below.
The first reason is the possibility of multiple of universes. Perhaps there are a very large number, maybe even infinite number, of universes, each of which has different values of the physical constants. Only a very small proportion of these would be able to support intelligent life, and we find ourselves in such a universe because we could not have been in any other.
To some people, the existence of an enormous number of universes seems highly implausible and the postulation of a divine creator seems more plausible. Some assert that Occams Razor favours an explanation that the universe was designed by a god over one with no god but billions of universes. This is entirely a matter of feeling though, not logic. I cannot rebut their assertion that to them it seems implausible that there should be an enormous number of universes. However, to me it seems entirely plausible. In some of my moods, it seems inevitable, almost obvious. At other times it seems less likely. Why should there be only one universe? There’s no answer to that question. It’s like asking “what’s the best number: one, a billion or infinity?”.
The Intelligent Designer hypothesis that is proposed as an alternative to multiple universes, seems more plausible to some, but far less plausible to me. Neither hypothesis can be defended or attacked on logical grounds, as we are operating in the territory of fundamental axioms (what seems plausible or self-evident). It’s just a question of which you prefer.
From a mathematical perspective (I always have to have one of those), if you view the number of universes as a random variable from some a priori Poisson distribution then the argument just becomes one about what you consider to be a reasonable frequency parameter λ for the Poisson distribution. Theists and Deists find an extremely low value of λ most plausible, in which case there would be only one or at most a handful of universes. Atheists are more likely to be comfortable with very large frequency parameters. Again, which you find more plausible is just a matter of inclination and cannot be proved or disproved.
A deeper reason for the values
But we don’t need multiple universes to explain the constants. We may one day discover deeper scientific truths that explain why the constants have the values they do. To me it seems most likely that this will indeed turn out to be the case and that these truths will emerge as part of a grand unified theory of everything, or on the way to one. I can imagine that theory explaining why it would be impossible for the constants to have any other values. This is speculation but again it’s just a question of what appears plausible to you. To me, this seems not only plausible but highly likely. In the absence of evidence as to what is true I like to believe what is beautiful and to me a universe in which the physical constants had values that appeared to be entirely random yet necessary would be ugly. An underlying pattern that explained why they had to have the values they have could be an aesthete’s delight.
What does ‘fine tuning’ mean?
Finally, I’d like to ask: who says the constants are finely tuned? The fine tuning knob on an AM radio might make adjustments of only 10kHz per revolution, whereas the gross tuning knob might adjust by 200kHz per revolution, and the frequency range for the AM spectrum might be about 700kHz, or more than three full turns of the gross tuning knob. (It’s a long while since I’ve had a radio with tuning knobs on, so forgive me if these numbers are not entirely accurate). We give the fine tuning knob its name because it only changes the frequency by a small fraction of the overall range for each turn of the knob.
But what is the range of possible values for the physical constants? If one of them has a value of 5.6321 and values that differ from that by more than 0.0001 in either direction would not allow life to develop then that is fine tuning indeed if the range of possible values is anything from 1 to 10, but it is very coarse tuning if the range of possible values is only 5.6320009 to 5.6321001. So far as I am aware, nobody knows what the range of possible values for these constants is, or even whether there is a range, so how can we say whether they are finely or coarsely tuned?
So, in summary, if the ‘finely tuned constants’ argument makes you feel warm and secure in an enhanced belief in your Intelligent Designer, that’s great. Just don’t mistake that feeling for a logical argument.