A social psychologist sometimes selects as his field of research attitudes and interactions which are invested with powerful personal implications and strong ideological connotations. If at the same time he is determined not to study them in isolation from the complex social systems in which they are produced, he is confronted by a number of difficulties, many of which are by no means merely methodological. Two of these difficulties are particularly important. One of them is that the trends of thought which dominate social psychology tend to conceive of interactions between individuals or between subgroups as if they were enacted outside of the framework of institutional and ideological systems; and yet it is the salience and the regulating power of these systems which determine the fact that we are dealing with ‘interactions’ rather than with something like ‘inter-reactions’. The second difficulty is that, in the course of their historical development and in order to ensure their survival, these systems had to attempt to gain their legitimacy. This has been the case even on the cognitive level in the sense that the institutional and ideological systems constructed models of explanation which would enable them to become socially accredited and long-lived. Consequently, the social psychologist often finds it difficult to resist the temptation to accept uncritically the explanatory models and concepts which these systems use in achieving their self-acceptance and their acceptance by others.