Darwin, Wright suggests, "was as much a symptom as a cause of the deism or epicureanism which then came to be associated with him." If you're an epicurean, Wright explains, then while there may be god or gods somewhere, they are a long way away and the key is that "this world has its own processes which are rumbling along, and so evolution is basically an epicurean idea--read Lucretius."
As a rationalist program, evolution tends to use its own axioms to judge all ideas. For example, design must be false because organisms are not optimally fit (a key evolutionary concept). This parochial tendency is common, and Wright points out how it works in the infra dignatatum argument:
Once god gets pushed out of the process, then of course what happens must happen from within rather than from outside. Then you can caricature the idea of divine intervention. Because if you're a deist or an epicurean you've got this distant god, who if he's going to do anything in the world would have to reach down and rather incongruously mess around, and then go away again.
And since this sort of dabbling was beneath god's dignity, naturalistic explanations were required. This was the infra dignatatum argument used by the early botanist John Ray and others more than a century before Darwin.
But the history of thought behind evolution is fairly complex, and Wright does not venture into all its depths. For instance, Kant's opposition to the renewed interest in epicureanism in modern times was, ironically, one of the factors that motivated him to call for a strictly naturalistic origins narrative. Beyond this, there were in fact a dozen or more metaphysical concerns that converged on naturalism as a requirement for any theory of origins. But Wright cogently articulates the big picture, and continues with this explanation of why Darwin's theory was so happily accepted:
This is why Darwin gets all the mileage that he does--because it is where people wanted to go. God can't tell us how to run the world, we'll run it our own way and then religion will be an escape from the world. ... The reason why people wanted to believe that stuff was not because they said "Oh my goodness, he's discovered some very interesting finches, this means we can't believe in Genesis anymore." ... I'm perfectly happy to say that species have evolved; I'm perfectly happy to say that that's how God was at work, and maybe is at work.
Indeed, there is nothing wrong with evolution, per se. After all, the species came about somehow, perhaps they evolved, somehow, some way. The idea is scientifically challenged and religiously motivated, but that doesn't mean it isn't true. But the idea that evolution might be true is not what Darwin and his followers are pondering. For them, evolution is mandated. It is a fact, and there is a world of difference.
What Wright comes ever so close to exposing, but does not seem to understand, is that the cultural mandate was not merely crucial in the motivation of Darwin's theory, but also in its justification. In other words, it is not as though there were these cultural-religious forcing functions, but then serendipitously the idea turned out to be a fact by virtue of compelling scientific evidence. No, the scientific evidence is interpreted according to our cultural-religious template. Theology is still queen of the sciences.
All those evolutionists who think they are free of religious influence, according to some great new "Enlightenment," are living a lie. They are the most dangerous of all, for their delusion of objectivity underwrites their self righteous indignation and vitriol. Religion drives science, and it matters.