Alfred North Whitehead (1861–1947) was the most sociological of philosophers. This in two ways: first, he viewed all enduring things as ‘societies’; second, he believed that one major role of theory is to challenge the deepest preconceptions and assumptions which permeate our attempts to understand and explain the world. What such claims mean and what their consequences might be will be considered throughout this book. Its overall aim is to outline Whitehead's philosophy; the challenges that it makes and the opportunities that it offers social theory with regard to a specific set of problems and concerns, namely those of realism and causation, value, subjectivity, the body, sexual difference and capitalism. Yet it must be stressed that Whitehead was a philosopher not a sociologist and his ideas are not to be envisaged as simply and directly applicable to social theory. He will not miraculously solve or explain away a set of conceptual problems relating to contemporary society or analyses thereof. Having said this, Whitehead's work has some fundamental implications for the status and procedures of social theory and social theorists which could lead to a reconceptualization of some of its founding claims and methods of analysis. Whitehead's philosophy constitutes a bold cosmological vision which diagnoses the fault lines of modernity and its conceptual apparatus by identifying what might be termed its “culture of thought”. It also offers a prognosis which might enable the production of novel, differently textured modes of thought.