Now there are three reasons for which you may co-operate with a man: because you love him, because you fear him, or because you hope to share the swag. These three motives are of differing importance in different regions of human co-operation: the first governs procreation, and the third governs politics.
Source:The advantages of cowardice. in: Mortals and Others; Bertrand Russell's American Essays, 1931-1935, v.1
More info.:http://russell-j.com/COWARD.HTM