Chapter 4 is the crux of The God Delusion. It's here that Richard Dawkins sets out to demonstrate, as the chapter heading states, why there almost certainly is no God.
His argument amounts to this:
Creationists (for Dawkins this is anyone who believes in God) hold that the world and life are astronomically improbable and therefore could not have come about on their own. Thus, the creationists believe, there must be an intelligence which lies behind it all, i.e. God. However, anything intelligent enough to create the world must itself be highly complex and therefore at least as improbable as the world it creates. Thus, if the improbability of the universe is so great as to render it inexplicable apart from a designer, then that designer, being even more improbable, must itself require an explanation. This leads to an infinite regress of "designers" which is an absurdity. Therefore, the simplest, most reasonable alternative to believing an absurdity is to believe that the universe is all there is.
Dawkins thinks this is a knock down argument against the rationality of believing in God's existence, but it fails for at least reasons:
1. The assumption that the source of complexity must itself be complex is false.
2. The argument from improbability is based on a category mistake.
3. The argument is based on the assumption that the theist is forced to accept an infinite regress.
4. The argument commits the fallacy of claiming that if there's no good reason to think an event didn't happen that it therefore almost certainly did happen.
We'll consider 1 and 2 today and 3 and 4 tomorrow.
Dawkins argues that if life is designed the designer must be at least as complex as what he designed and therefore at least as improbable and therefore at least as much in need of an explanation for his complexity.
Yet Dawkins believes that the ultimate source of the universe and all the complexity it contains was a simple, homogenous point (singularity) which, in the Big Bang, ultimately produced the present world. He also believes that the first cell to appear in the long chain of living things was far less complex than the myriad life forms into which it has evolved. He also believes, I assume, that the zygote which gives rise to an adult human is much less complex than the adult it gradually forms itself into. So, it's not clear to me, in light of these examples, why he would stake his argument on the claim that complexity can only be generated by even greater complexity. The assertion seems to be just false.
If God is simple, as many theologians and philosophers believe, then Dawkins' claim that he's even less probable than the universe comes to nothing. But this is a relatively minor point. The second - and I think the greatest - problem with Dawkins' argument is that it uses the idea of improbability in an ambiguous and logically illicit manner.
When we say that the complexity of the living world is improbable we mean that it is unlikely that it could have arisen solely by unguided processes. We mean that it is astonishing that it would have just happened by coincidence, without any purposeful input. It is highly improbable, for instance, that a stick would appear to be whittled to a point if only mechanical forces ever acted upon it, but it's not at all improbable that the stick takes on this appearance given the existence of a boy with a knife.
In other words, complex universes containing complex living things are improbable only on the assumption that they arose by sheer chance. They're not at all improbable if there's an intelligent agent involved in their origin.
Moreover, although it's indeed highly improbable that complex things like cells and universes could be produced by purely mechanical processes, God, unlike the boy with the knife, is not something which is produced. God has for centuries been thought of by philosophers as a necessary being, one which does not depend on anything else for his existence. Thus, it is a category mistake to talk about the improbability of God coming to be in the same sense that the universe comes to be. It is the origin of the universe and the origin of life that beg for a causal explanation. God is not the sort of thing that has an origin and therefore not the sort of thing which depends upon some cause outside himself and not the sort of thing to which the term "improbable" applies.
The universe can be defined as the sum of all contingent entities. Contingent entities require a necessary entity as their ultimate cause. This ultimate cause of the constituents of the universe cannot itself be contingent (dependent) upon anything else or it would, by definition, be part of the universe. Thus the ultimate cause must be something which does not "come to be" and which exists entirely independently of any contingent entity. It must have necessary existence.
Dawkins doesn't seem to understand the distinction between necessary and contingent being. If he did he wouldn't confuse God with contingent entities. When the difference is understood, the argument from improbability, in which he invests so much, collapses.
More on Dawkins' argument in chapter 4 tomorrow.
RLC