Dawkins presents an improbability argument against the existence of God.
The idea, I take it, is that the fact that God is supposed to be a conscious, knowing, intelligent designing subject means he is himself very far from being “simple”. He must be terrifically sophisticated and complex, in fact.
(i) invoking God to explain complex things like eyes, fine-tuning, etc merely replaces one improbable thing by another (overall, improbability is not reduced), so undercutting the justification for invoking him, and
(ii) God's being highly improbable, it’s highly unreasonable to believe in him, given the absence of evidence for God.
While I, like Dawkins, am not persuaded by intelligent design arguments (and let me stress I am generally in agreement with Dawkins, and in fact am a great admirer of his), I am not sure Dawkins' improbability argument is correct.
Prof Hugh Mellor (philosophy, emeritus, Darwin College, Camb.) distinguishes objective (or, as he puts it, physical) probability and epistemic probability.
The physical probability of an event etc. is the chance of it happening, given certain facts/laws. So, the physical probability of this unloaded dice rolling a six is one-in-six, of it raining today, given the general conditions (high pressure, etc), is very low, and of my dying before I reach 150 is very high.
The epistemic probability of a claim etc. is the probability of its being true, given the evidence. So given the patter against the window, the wet feet of the shoppers, etc. the probability of its currently raining is high. The evidence is good.
Things can be objectively improbable but epistemically highly probable. That this coin landed exactly on its edge is epistemically very probable (I just saw it happen with my own eyes) yet objectively improbable (the chance of it happening, given certain laws/initial conditions, is v. low)
It seems the reason we find things shocking, surprising and standing in need of explanation is that their objective probability seems very low. If someone lives to 300, or if it snows midday in the Sahara, or if my left foot spontaneously combusts, or if a coin lands exactly on its edge, we’ll be amazed, and look for an explanation. An explanation that lowers the improbability of the event (or even shows that it had to happen).
Notice that its objective probability we are talking about here. You can’t explain an event by raising its epistemic probability. I can confirm beyond any reasonable doubt that my left foot has indeed spontaneously combusted. That doesn’t remotely explain why it spontaneously combusted. Here's Mellor making the same point:
Take the probabilistic link between smoking and cancer. My smoking will only explain my getting cancer, if I do, by making it more probable, if that probability is a real physical probability (or chance for short). It is not enough for my smoking merely to raise my cancer’s so-called epistemic probability, the kind of probability that measures how far evidence supports a hypothesis. After all, that probability is also raised by the symptoms which tell my doctor that I have cancer. But these symptoms do nothing to explain my getting cancer, because they are not what raised the chance of my getting cancer in the first place.
Now design arguments for God work by pointing out that something is allegedly objectively/physically improbable, and then explain it by invoking God to reduce that improbability.
Mellor, however, suggests that, when it comes to, say, the character of the universe, it has no objective probability, high or low. Because that would be a physical improbability. And a physical probability is always relative to whatever the physical laws and initial conditions are. So…
the initial state, if any, of a universe, or of a multiverse, which by definition lacks precursors, has no physical explanation, since there is nothing earlier to give it any physical probability, high or low.
Similarly, God would have no objective/physical probability, high or low, on Mellor’s view. It's only things within a given universe that have such physical probabilities.
I suspect Mellor may be correct. That the universe has these laws etc. is neither probable nor improbable, objectively speaking. Nor is there anything remotely surprising - or standing in need of explanation - about it's having just these laws.
Certainly, there's a question here for Dawkins - is God objectively improbable? Or is he neither probable nor improbable, as Mellor would, I think, maintain?
Notice, by the way, Paley's example of the inference about the watch is not threatened by all this. A watch found on a beach is hardly something that purely natural mechanisms are likely to have produced all by themselves. Its spontaneous appearance really is physically improbable, given the laws of nature, etc. So we are justified in invoking an intelligent designer.
But the logic doesn't carry over to fine-tuning. From Dawkins' perspective, the problem with invoking God to explain "fine-tuning" (the universe's laws and initial conditions being "just right" for life) is that we are invoking an improbable thing to explain an improbable thing. From Mellor's perspective, the problem is that the "fine-tuning" is neither probable nor improbable, and so doesn't require an explanation (by means of God, a multiverse, or anything else).
Mellor's paper supplied on request.