Steven Pinker's new book on rationality came out today. I figured someone on LessWrong would write a review for it, so I might as well be the one to do it.

Unlike Pinker's prior books, such as The Blank Slate and The Better Angels of Our Nature, this book lacks a straightforward empirical thesis. Instead, he mirrors the sequences by building a science of rationality and then tries to convince the reader that rationality is important, both personally and socially.

Unfortunately, long-time readers of LessWrong are unlikely to learn much from Pinker's new book; his content is too similar to the content in the sequences. An upside is that Pinker's treatment is more concise, and his style more closely resembles mainstream thought. Consequently, I'm tempted to recommend this book to people who might otherwise be turned away by Rationality: From A to Z.

He starts by asking a simple question: how come it seems like everyone is so irrational? Pointing to religion, conspiracy theorists, ghost-believers, anti-vaxxers, alternative medicine adherents, and postmodernists, Pinker makes a good case that there's a lot of irrationality in the world. On the other hand, he continues, shouldn't humans have evolved to be more rational? How could such persistent, widespread irrationality be so common in humans, if our survival impinges on our ability to reason?

Pinker provides a simple answer: humans are very rational animals, just not in every domain. In those domains on which our survival depended, such as finding and eating food, humans are much less clueless than you might have been lead to believe. Pinker provides the example of the San people of the Kalahari Desert in southern Africa, who, despite their mythological beliefs, are stunningly successful at hunting prey. He cites Louis Liebenberg, who documented how the San people use Bayesian reasoning to hunt, applying it to footprints and animal droppings in order to build an accurate picture of their natural world: a dry desert on which they have subsisted for over a hundred thousand years.

It's not hard to see this dual phenomenon of rationality and irrationality reflected in the modern day: many young Earth creationists believe that the moon's craters were literally planted by God to give the appearance of old age, but these same people rarely apply the same standards of reason to matters in their ordinary life.

Yet, as Pinker o...

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