Richard Dawkins has a dilemma when it comes to design arguments. On the one hand, he maintains that it was Darwin who killed off design and so implies that his rejection of design depends upon the findings of modern science. On the other hand, he follows Hume when he claims that appealing to a designer does not explain anything and so implies that rejection of design need not be based on the findings of modern science. These contrasting approaches lead to the following dilemma: if he claims that Darwinism is necessary for rejecting design, he has no satisfactory response to design arguments based on the order in the laws of physics or the fine-tuning of the physical constants; alternatively, if Humean arguments are doing most of the work, this would undermine one of his main contentions, that atheism is justified by science and especially by evolution. In any case, his Humean arguments do not provide a more secure basis for his atheism because they are seriously flawed. A particular problem is that his argument for the improbability of theism rests on a highly questionable application of probability theory since, even if it were sound, it would only establish that the prior probability of God’s existence is low, a conclusion which is compatible with the posterior probability of God’s existence being high.