Following a brief analysis of theory and of sociology as the explanation of patterns of social impact, the major forms of sociological theorizing are critically reviewed. These are identified as correlational theory, sequence theory, and grand theory or verbal model-building. The basic features of process theorywhich is taken to be most faithful to the objectives of theorizing and to the fundamental problems of sociology-are sketched in terms of opportunity variables, motivation and social perception variables, and social reinforcement variables. Applications of process theory are suggested in the areas of internal migration, suburban ecology, and deviance in complex social systems. Finally, sociologists are urged to focus on key theoretical problems, rather than empiricism or blatant ideologies. Almost any judicious review of sociology during the past sixty or seventy years would probably conclude that we have developed a highly sophisticated set of methods and techniques and a tremendous storehouse of empirical investigations in a great variety of settings. But in the realm of theory-that third and most significant aspect of any mature field-sociology has been inconsistent and often disappointing. Certainly, theorizing has received more attention in the past twenty years, but much of this has been prescription, exhortation, and preparation, rather than dedicated execution and serious revision or refinement (Faris, 1964; Gross, 1967; McKinney and Tiryakian, 1970). As one more or less identified with theorizing as a crucial segment of the sociological enterprise, I perhaps run the danger of being called a traitor to theory or even a perennial malcontent. But I hope to make clear that my criticisms are prompted by the gap between the immense potentialities of sociological theory and the implicit limitations we have generally imposed on our performance in the service of theory. Obviously, such criticisms also rest on notions of adequate theorizing and, even more3fundamentally, on a conception of sociology itself. Since both of these tasks are major enterprises in themselves, I shall have to resist temptation-and an epidemic of righteous indignation among the audience-by presenting only very brief and unavoidably arbitrary remarks on each in turn. First, let us assume that the primary task of sociological theory is to provide a testable (demonstrable) explanation of the development, persistence, or change of some category of social phenomena. Certainly, prediction is also important, but prediction normally involves greater concern for probability of outcomes than for an understanding of the ways in which these phenomena are produced. Explanation is a continually elusive and difficult objective-one that entails elegant logical and imperfect practical achievements. For present purposes, however, explanation consists of the operations by which interactions between variables are specifiednormally by attending to the effects of intermediary, intervening, and control variables (Doby, 1969; P. Park, 1969; Popper, 1963; Stinchcombe, 1968). With this in mind, the criteria of a fruitful sociological theory are fairly evident and longaccepted, though I would include some partially