This dissertation is centered around questions concerning the social (social ontology) and its relationship to social research. One of its major reference points is the philosophical system (characterized as emergentist systemism in this dissertation) developed by the accomplished Argentinian-Canadian physicist and philosopher Mario Bunge. This dissertation draws extensively on the research findings of natural and social sciences, both in America and Europe, to argue for a systemist (i.e. transcending both macro- and micro-reductionism), realist, and critical approach to social ontology. In particular, Luhmann’s, Bunge’s, and critical social systems theorists’ formulations of social ontology, as well as Luhmann’s premature shift of focus from ontology to epistemology, are discussed and evaluated in depth. The approach developed in this dissertation is also extended to contribute to the wider debates within sociological theory and analysis, including the project of analytical sociology (as advanced by, among others, Peter Hedström and Jon Elster), critical realism, reductionism, emergence, micro-macro link, social structure and human agency, dialectics of nature, and causality and mechanism-based (microfoundational) explanations in social science.