The distinction between rationality and irrationality in the Western tradition goes back at least to Aristotle (1976, p. 90), who wrote that the “irrational part of the soul” is persuaded and admonished by the rational part “in the sense that a child pays attention to its father.” It is all too easy to say that this distinction is misleading or at the very least simplistic. For example, there seems to be a neurological connection between emotion and decision making in human beings; this is suggested by the phenomenon of people who, as a result of prefrontal brain damage, become both emotionally unresponsive and bad at making everyday decisions, even though their “pure reasoning” abilities, as measured by standard intelligence tests, for example, are undiminished (Damasio 1994).
Compared with the great complexity and richness of individual and social life, simple distinctions are by definition crude. But the standard argument is that to understand the social world in any generality, if one has ambitions other than chronicling infinite detail, one must use simple and crude concepts; for example, this book employs a very simple conception of individual thought and action and applies it widely. Theories and explanations can thus be much more clearly demarcated than reality itself. For example, although few would say that there is a clear distinction between the “rational part” and the “irrational part” of a human being, it seems obvious that there is a distinction between explanations based on rationality and explanations based on irrationality or nonrationality; Vilfredo Pareto institutionalized this distinction, calling it the dividing line between economics and sociology (see Swedberg 1990, p. 11).
This distinction, related to a whole series of distinctions,