From a philosophical perspective, the mid 19th century (as we all know, Darwin’s era) is an interesting place; not least of all with regard to the notion of the ‘God of the gaps’. This essentially underpinned academic theology in that era – ultimately that whatever could not be understood through reason/logic/scientific enquiry, could always be explained by the existence of God, and there would always be things in the world that could not be understood through reason and science. Although it was clearly more sophisticated than this, the balance between early-modern theology and a post-Enlightenment expanding and increasingly scientific understanding of the natural world was held by the ‘God of the gaps’.
It was and is a fragile basis for faith in God and does nothing to resist the onslaught of scientific evidence and leaves the person clinging on to the theory looking foolish. It is also precisely the kind of theology that Darwin himself encountered when studying to become an Anglican priest. This is the theology that he rejected, although it is still distinctly visible in his reasoning.
That is, that when looking for a theory of how to explain the gap between fossil A and fossil B, instead of saying that God was responsible for it, he postulated a theory that explained the transition from A to B: evolution. There was still a gap between the two, and a theory that explained the gap between the two. He had no evidence to substantiate his theory, other than the species/fossils which were given a gap of millions of years in order for evolution to take place. In other words, the theory of evolution is an atheist’s ‘God of the gaps’. Nobody has seen a species evolve and there is no evidence on the scale of a spherical earth versus a flat earth or environmental destruction versus denial, to truly support it. The only real evidence is the theory itself, but because the theory is so persuasive, it attracts apparently intelligent thought. It is harder to think of a greater delusion.