The Mismeasure of Man is a 1981 book written by the Harvard paleontologist Stephen Jay Gould (1941–2002). The book is a history and critique of the methods and motivations underlying biological determinism, the belief that "the social and economic differences between human groups—primarily races, classes, and sexes—arise from inherited, inborn distinctions and that society, in this sense, is an accurate reflection of biology." The book also critiques the principal theme of biological determinism, that "worth can be assigned to individuals and groups by measuring intelligence as a single quantity." Gould discusses two prominent techniques used to measure such a quantity, craniometry and psychological testing. According to Gould these methods suffer from "two deep fallacies." The first fallacy is of reification, that is, "our tendency to convert abstract concepts into entities." These entities include IQ (the intelligence quotient) and g (the general intelligence factor), which have been the cornerstone of much intelligence research. The second fallacy is one of ranking, or our "propensity for ordering complex variation as a gradual ascending scale." The Mismeasure of Man skeptically investigates "the abstraction of intelligence as a single entity, its location within the brain, its quantification as one number for each individual, and the use of these numbers to rank people in a single series of worthiness, invariably to find that oppressed and disadvantaged groups—races, classes, or sexes—are innately inferior and deserve their status." The book's second edition (1996) was revised to challenge the arguments of Richard Herrnstein and Charles Murray's The Bell Curve, which generated much controversy.