The basic frame of reference is in principle applicable to the hypothetically isolated actor in a nonsocial situation. In a situation in which a plurality of actors are in interaction, the scheme must be further differentiated to take into account the fact of complementarity of expectations — but this involves no modification in the basic frame of reference, merely a more elaborate deductive treatment. The pattern variables had previously been developed in a less systematic fashion in connection with the analysis of certain concrete problems of social structure. Preliminary consideration of the pattern-variable scheme in relation to these two types of system also revealed the symmetrical asymmetry of its application to personalities and to social systems. In the social system too the concept of mechanism is introduced because of its relevance in dealing with the dynamic aspects of systemic problems, particularly the problems of allocation and integration.