Methodological Individualism

58 Psychologism in early social scienceknowledge and what kind of psychological knowledge it is. Whether it should bebased on detailed knowledge about human behaviour derived from the science ofpsychology, or upon some simple assumptions derived from common sense.I suggest that we make a distinction between thin and thick versions of psychologism.Thin psychologism is minimalistic, and makes use of very simplepsychological assumptions, like those about economic man. It does not rely onany acquaintance with the science of psychology. Thick psychologism, on theother hand, makes use of more detailed knowledge about the motives andreasoning of human beings. An important source of this more sophisticatedknowledge is, of course, the science of psychology. The psychologism of Paretowas a thin version of this doctrine.Pareto’s main contribution to individualism, was not his psychologism, but hisdenial of the possibility of interpersonal comparisons of utility and his famousidea of optimality, commonly called Pareto optimality, or Pareto efficiency. Thelatter idea is one of the central pillars of the individualist tradition in normativeeconomics and political philosophy. Its basis, the denial of the possibility ofcomparing the utilities of different individuals is also a characteristic mark ofindividualism, but not of utilitarianism (despite the fact that Jevons also deniedthis possibility). Among economists, it is typically the most outspoken methodologicalindividualists, the Austrians, who deny the possibility of comparing theutility of different individuals. The reason, of course, is that it blocks the possibilityof constructing a collective utility-function and, more importantly, of acollectivistic politics, based on such a utility-function. The intellectual roots ofthis view are, I believe, in German qualitative individualism, which is a source,not only for Austrian individualists, but also for Pareto (cf. Carroll, 1973).German psychologismIn chapter 1, we saw that thinking about the individual and society in nineteenth-centuryGermany was dominated by historicism. It is perhaps paradoxicalthat the science of psychology should first emerge in this intellectual context, andthat it should take the form of a natural, rather than a human, science.Nevertheless, it did, but not without a fight. The natural and experimentalscience of psychology met with strong resistance from the start and, in the end,there was a split between an experimental and explanatory psychology, on theone hand, and a phenomenological and descriptive psychology, on the other.The latter was conceived of as the foundation upon which all human sciencesrest. The implication was a kind of psychologism, that was the most commonversion of methodological individualism in sociology (see chapter 5) before therise of rational choice sociology (see chapter 10).The rise of psychologyIt is commonly agreed that psychology as a science, or at least as an academicdiscipline, originated in Germany in the middle of the nineteenth century. It had