ABSTRACT
This chapter extracts from Vilfredo Pareto's sociology micro-models whose significance has been neglected or underestimated, precisely because they were less explicit in the Trattato. It concentrates on the sole issue of the rationality of beliefs, or more precisely, collective beliefs. The chapter brings attention to certain important limitations of Pareto's general account of collective beliefs. Pareto's sociological theory is sometimes called "irrationalist" to signal its extremist stance, in which reason does not play any role. Actually, the theory of dissimulation is more often attributed to Pareto than the theory of expression. The chapter claims that sociological theory is the most original part of Pareto's general theory of collective beliefs. It describes that this theory becomes stronger still if one introduces John Stuart Mill's psychological views, which are more refined. The chapter concludes, only two limitations to Pareto's theory — or rather theories, since Pareto's account of collective belief is not systematic
