The core idea of analytical sociology is the importance of mechanism-based understanding of social processes. Sociological theories should provide clear and precise accounts of the social mechanisms by which the intentional activities of social agents bring about social phenomena. Theories about social mechanisms can be characterized as theories of middle range as they provide clear, precise, and simple explanations for specified aspects of range of different phenomena, without pretense of being able to explain all social phenomena. Intentional action plays an important role in social mechanisms, but the analytical sociology perspective suggests that our account of human agency should be based on findings and theories of psychological and cognitive sciences rather than on some preconceived ideas about human motivation or cognitive processing. Much of the development of mechanism-based knowledge consists of developing how-possibly explanation schemes. Agent-based computer simulations can be very useful for this kind of endeavor.