This book presents a set theoretical approach to sociological research. It revisits existing sociological approaches and discusses their limitations, before suggesting an alternative. While the existing canonical approaches of Positivism, Conflictualism, and Pragmatism are based on biology, history, and physics, respectively, the set theoretical approach is based on mathematics. Utilising its philosophical exploration delineated by Alain Badiou, the book further translates his work into the field of social science. The result of this translation is termed Multiplitism, which evades the limiting contradictions of existing approaches. Drawing on the mathematical notion of ‘set’ and relating it to recent sociological turns such as the relational and the ontological, the book proposes a scale-relativity through which the researcher (as subject) and the researched (as object) are integrated. The book will be of interest to social scientists, particularly social theorists and advanced level students.