Each major ideology consists of broad, general, enduring assumptions, while that of each member of the group identified with it comprises also assumptions peculiar to place, time and circumstance; no member holds exactly the ideology of the group. Each of them stands closer to that than to the ideology of any other group, but every one of them differs from it, and since ideology governs purposeful behaviour this has the effect that the behaviour of the group differs from that of of each member. The group does things done by none of its members. This conception, of a whole doing things done by none of its parts, sometimes evokes surprise, even incredulity, yet the event commonly occurs and can be easily illustrated.
Take a fleet of sailing boats making for a point to the north. The wind comes from that direction and they can’t sail directly against it, they have to tack. So some start off northwest and then turn northeast, while others start off northeast and turn northwest. Each movement comprises a northerly component and these overlap, strengthening each other, while the westerly and easterly components tend to cancel out. The fleet moves due north although not one of its parts ever does so. In much the same way, an ideological group is affected by the assumptions which its members hold in common, rather than by those on which they differ.
from Ideological Commentary 57, August 1992.