Sociological theory, if it is to advance significantly, must proceed on these interconnected planes: (1) by developing special theories form which to derive hypotheses that can be empirically investigated and (2) by evolving, not suddenly revealing, a progressively more general conceptual scheme that is adequate to consolidate groups of special theories (1968, p. 51).

We sociologists can look instead toward progressively comprehensive sociological theory which, instead of proceeding from the head of one man, gradually consolidates theories of the middle range, so that these become special cases of more general formulations (1968, p. 51).