Page 4 begins a list of arguments in favor of the closed mind, each with a rebuttal. I don't agree with any of the arguments for the closed mind, but I also don't agree with some of the rebuttals. Some comments and criticisms follow:
#1 Rebuttal relies on evolutionary psychology which is false.
#2 Assumes we have to continue to believe refuted ideas in order to continue considering them. We don't. We can take a more sophisticated view that something is both refuted and worth trying to save (create a related idea that isn't refuted), without actually believing the refuted idea.
#3 Rebuttal is too weak and concedes too much. It concedes that people can get stuck in frameworks but points out that not everyone will. A better answer is Popper's criticism of frameworks in The Myth of the Framework; we don't need to make concessions here.
Also the rebuttal says "the Sapir-Whorf hypothesis has been shown to be false" but doesn't include any source nor enough explanation to judge or criticize this idea well; apparently the reader is intended to believe there is persuasive, unspecified research on the matter and take it on authority.
#6 I'd add that faith doesn't guarantee a closed mind since it's well known that people sometimes lose faith.
#8 This badly misrepresents Dawkins' view and is false. In The Selfish Gene, when introducing memes, Dawkins did not say memes are mind-viruses. He explained a meme as a unit of cultural transmission, and replicator, and gave various examples and explanations making it clear that they can be good or bad, and the concept doesn't have anything built-in about memes exercising control over humans.
#9 The crucial point here is that just because people make mistakes does not imply that can't learn better.
I'm up to page 24 now. I think the book so far mixes up arguments. It argues two different things at different times: 1) all people are not literally 100% closed minded. 2) most people are significantly open minded and can learn things and make progress in real life in practice
(1) is easy to argue for and true, but (2) is what people care about. (2) is a bit vague but would be true if elaborated in a reasonable way. The book states (1) as its thesis and keeps repeating it and arguing for it, but then at other times the argument for (1) is trivial but it spends time arguing for (2), apparently because (1) isn't enough.
Page 24 asserts both Ayn Rand and Marx as examples of people who wanted to spread their ideas without any criticism allowed, like leaders of religious sects. That's insulting, offensive and unargued.
The book generalizes about people too much. Example on p 25:
People prefer to adopt and spread ideologies that: [list of 6 criteria]Some people use those criteria and some don't. People can and do invent all sorts of criteria. People aren't all the same and don't have all the same preferences, values or ways of thinking.
Page 25 also locks in claims about how evolution shapes our thinking as part of books main point. This is elaborated on p 28 with statements like
Evolutionary psychology shows us that...Note that this and many related assertions are unsourced.
Page 200 tells us that it would be "impossible" to understand Ayn Rand's ideas about art, morality or metaphysics from her novels, without reading her non-fiction. The novels only explain classical liberal ideas "identical" to those of Herbert Spencer and Ludwig von Mises.
The "impossible" and "identical" claims are silly. While similar, her politics aren't identical to those others. One reason is that you can't completely separate politics from morality and Rand's morality is different. More mundanely I'm not aware of Mises proposing an end to coercive taxation as Ayn Rand did. And according to Wikipedia Spencer opposed land being private property so that's very different!
Regarding "impossible", it's hard, certainly, to understand Objectivism without studying it carefully, but the novels have a lot of information and if you thought about it a lot why couldn't you learn more from them than Percival allows for? What's to stop you and make it *impossible*? Take Rand's morality. She does explain and illustrate a lot about that in her novels. I'd say her novels are the *best* source for learning her morality. Why does Percival -- who apparently dislikes Ayn Rand even though her philosophy has a great deal in common with Popper's -- choose to make such strong and negative comments about her in passing?