Dennett attempts to look at Darwinian evolution through the eyes of what he sees as a persistent explanatory paradigm: the notion of species creation through special design. He begins by looking, briefly, at the views of Hume and Locke. Though they touched on the abstract possibility of variety through chance and time, they weren't able to conceptualize the mechanism and so abandoned it. They settled on the conclusion that an intelligent artificer had to create the specificity we see in the world because no unintelligent mechanism for doing so exists.
Dennett seems to have a sub-goal in this chapter of dismantling any vestiges of non-Darwinian explanation but does so mostly through assertions rather than argument as would be expected in an early chapter like this. Little is given evidentially in this introductory chapter but Dennett does create a certain level of anticipation for what is coming.
With regards to the possibility of Darwinism being wrong he writes, "There are vigorous controversies swirling around in evolutionary theory, but those who feel threatened by Darwinism should not take heart from this fact. Most--if not quite all--of the controversies concern issues that are 'just science'; no matter which side wins, the outcome will not undo the basic Darwinian idea." (19)
Additionally, he says that the "Darwinian Revolution" will be as much a part of the consciousness of educated people as Copernicus' theory. "In due course, the Darwinian Revolution will come to occupy a similarly secure and untroubled place in the minds--and hearts--of every educated person on the globe, but today, more than a century after Darwin's death we still have not come to terms with its mind-boggling implications." (19)
Dennett also uses terms that describe Darwinian evolution (or perhaps more accurately, the neo-Darwinian synthesis) as fairly close to certain.
"The fundamental core of contemporary Darwinism, the theory of DNA-based reproduction and evolution, is now beyond dispute among scientists." (20)
"It took an irresistible parade of hard-won scientific facts to force thinkers to take seriously the weird new outlook that Darwin proposed. Those who are still ill-acquainted with that
beautiful procession can be forgiven their continued allegiance to the pre-Darwinian ideas. And the battle is not yet over; even among scientists, there are pockets of resistance." (21)
"You can either deceive yourself or let others do the dirty work, but there is no intellectually defensible way of rebuilding the might barriers to comprehension that Darwin smashed." (25)
In this chapter, Dennett is essentially setting up his book. There's very little if anything by way of substantive evidence for evolution and, in fact, pits Darwinism against theistic special creation.