David McLellan presents case studies of Simone Weil, Reinhold Neibuhr, liberation theology, and the Green movement in an attempt to demonstrate an intimate connection between politics and the Christian religion, arguing that such a connection is both inevitable and desirable. After briefly reviewing the classical political theoretical tradition, McLellan explores how the conservative political thought of Simone Weil flowed from the concept of the distant, transcendent God of her Platonised Christianity. By contrast, Reinhold Niebuhr used theology to interpet experience, which gave a philosophical and theological depth to his support of American liberal democracy. For him, the United States was a dynamic spiritual reality. Liberation theology presents the tightest connection between religion and politics with the view that God's action in history is manifest as God acts to empower the poor. Finally, McLellan surveys the Green movement which claims to transcend existing Western political traditions.
Here he compares the two creation stories in Genesis - one emphasising dominion, the other stewardship - to illustrate how the Judeo-Christian tradition has structured our understanding of nature. Central to the thesis of "Unto Caesar" is McLellan's argument that religion is not solely a dependent variable but has some substantial influence at times on the society in which we live and therefore is a fitting subject of interest for all, whether they are believers or not.