Render unto Caesar the things that are Caesar's and to God the things that are God's: every Christian, during his earthly pilgrimage, is bound by both the temporal and the spiritual authority, by the Church and by the state. The conflicting claims to jurisdiction posed by this double allegiance have, over the centuries, given rise to bitter and protracted controversies, often with profound and far-reaching consequences. It is the aim of the present work to set all of this into clear focus with a brief, readable yet accurate account of the Church-State relationship as it has developed from the earliest days of Christianity to our own time.