Abstract
Comparative research on social capital assumes interpersonal and institutional trust as central components of social capital. Using standard questions on trust in a number of longitudinal surveys such research has shown: 1) weak correlations between focalized and generalized interpersonal trust; 2) weak correlations between interpersonal trust and institutional trust; 3) weak correlations between trust and partecipation in associations. In this paper these empirical results are critically analyzed with the aim of making explicit the underlying theory of trust. More specifically, the nature of people who place their trust in strangers and of trust diffusors have been studied with the purpose of defining a policy of trust.