This broad and mediocre survey of psychology of people who stand out in history probably contains a fair number of good ideas, but it’s hard to separate them from the many ideas that are questionable guesses. He’s inconsistent about distinguishing his guesses from claims backed by good evidence.

One of the clearest examples is his assertion that childhood adversity builds character. He presents evidence that eminent figures were unusually likely to have had a parent die early, and describes this as the “most impressive proof” of his claim. He ignores the possibility those people come from families with a pattern of taking sufficiently unusual risks to explain that evidence.

In other places, he makes mistakes which seemed reasonable when the book was published, such as “Mendelian laws of inheritance are blind to whether an individual is first-born or later-born” (parental age has a measurable effect on mutation rates).

He avoids some of the worst mistakes that a psychology of history could make, such as trying to psychoanalyze individuals without having enough information about them.

He mentions some approaches to analyzing presidential addresses and corporate letters to stockholders, which have some potential to be used in predicting whether leaders have the appropriate personality for their jobs. I wonder what would happen if many voters/stockholders demanded that leaders pass tests of this nature (I’m assuming the tests can be scored objectively, but that may be shaky assumption). I’m confident that we’d get leaders with rhetoric that passes those tests. Would that simply mean the leaders change their rhetoric, or would it be hard enough to maintain a mismatch between rhetoric and thought patterns that we’d get leaders with better thought patterns?