In general, D'Souza's treatments are insightful, perceptive, and outstandingly well-reasoned. Thus it is all the more startling when--on one or two issues--he displays a lack of comprehension of the facts and a rather sophomoric reasoning. The prime example comes in chapter thrirteen, titled "Paley was right: evolution and the argument from design." In this section, D'Souza acknowledges his acceptance of the macroevolutionary story (albeit without the naturalistic component) and offers four reasons for that acceptance. It is here that he betrays himself as "in over his head" regarding the relevant facts and (as a result?) unable to think as clearly on this issue as he does elsewhere.
So, I'll address D'Souza's four arguments in favor of evolution (taking only the first in this post). He writes,
I am not a biologist, but what impresses me is that virtually every biologist in the world accepts the theory of evolution. While the debate goes on, it seems improbable that the small group of intelligent design advocates is right and the entire community of biologists is wrong.Having read some really perceptive arguments in the previous chapters, I almost couldn't believe what I was reading here! I would hope that every freshman philosophy student would (first of all) recognize this argument as fallacious. The truth value of a claim (or theory) does not lie in its popularity, and such an appeal to popularity is irrelevant to determining truth. This informal logical fallacy has a name--the ad populum fallacy--and is among the easiest to spot. I still find it incredible that D'Souza's defense of evolution begins with such a glaring error in reasoning.
This claim also betrays D'Souza's ignorance of the history of science. Many have been the times when virtually all scientists believed a wrong theory; and in each case, the acceptance of a better theory began with a few (or a single) scientist(s) boldly challenging the popular view. Before Einstein, "virtually every" astronomer and physicist accepted the idea that the universe was eternal and static. Einstein himself was so persuaded by that view that he distrusted his own equations (since they led to a contrary conclusion). He inserted a fudge factor of sorts (a cosmological constant for which there was no evidence) that had the effect of negating the expansion of the universe, thus preserving the static, eternal picture of the universe. Einstein later called this the greatest mistake of his life, and we now recognize that "virtually every" scientist of that day was dead wrong on that issue.
Any number of other cases could be cited. The fact is that major paradigm shifts within science always begin with a handful of intrepid, truly objective scientists skeptical of the reigning (popular) paradigm.
D'Souza's argument also spotlights his ignorance of the sociology of science. The extent to which it appears that all biologists accept evolution is in large part an artifact of the stranglehold that naturalistic neo-Darwinism has on the sciences in general and biology in particular. The expression of even the slightest doubt about evolution can result in the loss of one's job or the denial of tenure. This is especially true of biologists, but the Guillermo Gonzalez case at Iowa State University demonstrates that it is not confined to biology. So D'Souza's claim has at least two sociological problems: one, belief in evolution has become a pre-requisite for success within biology (despite its relative uselessness in practical terms), and two, those biologists skeptical of evolution dare not voice that skepticism (with the result that one might be fooled into thinking that virtually all biologists accept evolution).
Perhaps more importantly, the claim is simply false. Many are the biologists today, in the United States and elsewhere, who do not accept macroevolution, and that for evidential (not religious) reasons. In point of fact, macroevolutionary theory in general--and natural selection acting upon random gene mutations particularly--suffers from having a dearth of supporting evidence. It is its metaphysical and atheistic implications and not evidence that has caused the popularity of (indeed, the religious zeal toward) evolution among scientists.
Last, a word about the philosophy of science. Had D'Souza ever read Thomas Kuhn's The Structure of Scientific Revolutions, he would recognize in today's debate an existing paradigm in its dying stages. In particular, the defense of macroevolutionary theory not by appeals to the evidence but by ad hominem attacks and attempts to silence or discredit its critics is characteristic of a theory unable any longer to withstand empirical and logical scrutiny.
Again, I highly recommend D'Souza's book. But he was ill-advised to address biological evolution, a subject on which his knowledge and reading is clearly shallow, narrow, and one-sided and about which, as a consequence, his otherwise crisp thinking lets him down badly.