Hitchens uses these quotes to create a segway into discussion of the roots of metaphysics from a religious standpoint. Hitchens believes, as do many (myself included) that the roots of religion come from early man's inability to explain the world around him. That cosmology and ontology, including creation stories, are simply the result of a great fabrication to come up with the best explanation possible while being completely unable to comprehend the scale of the natural world. Because of the level of understanding we now hold of the world around us, Hithcens speculates that no attempt to bring faith and science to a amiable working relationship is doomed from the outset.
He preempts the usual objection of all the scientists of history, (and today) who are theists, by making sure we understand as a reader that someone like Newton being a brilliant scientist did not make him infallible, and that he was in fact a mystic and alchemist along with being a brilliant scientist.
Indeed, this is in fact a common fallacy that creationists love to bring up more than any other group using Newton and Darwin as examples. They will often point out the theistic beliefs of Newton, or target Darwin as a racist because of the full title of The Origin of Species. It's a twisted appeal to authority that has never really worked except on the dimmest of skeptics. Attacking the attitudes and such of someone says nothing about the accuracy of their science. James Watson, a mapper of the dna molecule is notoriously a racist, but that doesn't make the DNA not a double helix. So it is with Darwin and evolution.
It seems the primary conclusion of Hitchens here that humanity has outgrown the need for a religious cosmology; we now know enough about our universe to be fairly certain that there did not need to be a creator.
This was a short chapter, but I'll close with Hitchens's response to Tertullian's "Credibile est, quia ineptum est,"(I believe it because it is absurd) as I think it one of the best ways I have ever heard faith criticized, and summed up very succinctly. A passage that I believe most theists would agree with, until the second you apply it to their beliefs:
"It is impossible to quarrel seriously with such a view. If one must have faith in order to believe something, or believe in something, then the likelihood of that something having any truth, or value is considerably diminished."