He usefully subdivides and defines various fears, anxieties, and angers in different subjects and contexts—biologically, psychologically, and socially. He also repeatedly identifies reasons for the tendency to overgeneralize. His scope is wide ranging, and he is historically and biopsychosocially informed about meanings of consciousness and of intelligences (referring to, for example, Binet, Simon, Spearman, Thurstone, Wechsler, Gardner, and many others). He has contributed well-known research on temperament, and in his discussion he ranges easily from animals to children to scientists and philosophers. Having for several decades been somewhat intimidated by Kant and his "Ding an sich" ("the thing itself," or "the pure essence of a thing"), I was pleased to read Kagan's citing, in useful context, the philosopher Hilary Putnam, who said that "when we talk of 'Ding an sich' we do not know what we're talking about."