Dilemma for Dawkins
Proof of the existence of Zeus would either verify the claim that “God exists” or it would not. It is not immediately obvious which side of this dilemma Dawkins would choose. If he granted that proof of the existence of Zeus would verify the claim that “God exists”, then he would have to toss out his definition of “God” (as being too narrow). On the other hand, if he denied that proof of the existence of Zeus would verify the claim that “God exists”, then his conclusion that “God almost certainly does not exist.” (p. 189), would fail to rule out the existence of Zeus and Satan, and perhaps dozens of other gods.

Ambiguous Conclusion

Another way of putting this point, is that the main conclusion that Dawkins puts forward at the end of Chapter 4 is ambiguous between a weaker and a stronger claim:

(W) It is almost certain that there is no god who is responsible for creating this universe and everything in it.
(S) It is almost certain that there is no god whatsoever.
Proving the weaker conclusion (W) would not establish atheism, because it leaves belief in non-creator gods (such as Zeus and Satan) untouched.

Proving the stronger conclusion (S) would establish atheism, because it eliminates not only the God of traditional theism (an all-knowing, all-powerful, and perfectly good person), but also eliminates other lesser gods, such as Zeus, Baal, Wotan, and Satan.

There is a third possible interpretation of Dawkins’ conclusion as well. We could simply ignore his somewhat confused attempts to clarify the word “God”, and interpret his conclusion in terms of a more standard definition:

X is God if and only if
(a) X is all-powerful,
(b) X is all-knowing,
and
(c) X is a perfectly good person.

Note, however, that this definition includes a normative condition: “X is a perfectly good person”. So, this meaning or sense of the word “God” runs contrary to Dawkins’ assertion that the question “Does God exist?” is a scientific question. Since science has no capacity for resolving normative issues (e.g. “Is Jesus a perfectly good person?”), science alone cannot answer the question “Does God exist?” if we use normative categories to define the word “God”.

Nevertheless, since the above definition is closer to the standard meaning or use of the word “God” (among theologians and philosophers in Western thought) than the definition that Dawkins puts forward, it is reasonable to ask whether Dawkins’ argument establishes his conclusion on this interpretation:

(N) It is almost certain that there is no all-powerful, all-knowing, perfectly good person.
Since it is more difficult to prove a stronger claim, I will first consider the possibility that Dawkins intends to only make the weaker claim (W) at the end of Chapter 4. If his argument supports the weaker claim, that will still be a worthwhile philosophical accomplishment (Dawkins would say: “scientific accomplishment”). If his argument does not support the weaker claim, then it certainly does not support the stronger claim (S) either, for the stronger claim implies the weaker one. Finally, I will consider whether Dawkins’ argument supports claim (N).