another important function of multiple memberships lies in their contribution to the growth of mutual trust. whether it is a question of economic activities or of political mobilization, committing resources to a joint initiative involving other actors is always, to some extent, risky. In each case, the route to mobilization requires actors to conduct some exploration of, ''investigative process'' with regard to (Diani 1995 a: ch.1), their environment, in search of trustworthy allies. This process is much simpler if there are ongoing links between the central activists of the various organizations concerned. This does not mean that other alliances are not possible, or even more frequent. But the relative cost of forging these other alliances will usually be higher, inasmuch as contacts between the different groups are not ''routinized'' through interpersonal connections.