“Of political principles,” says a distinguished authority, “whether they be those of order or of freedom, we must seek in religious and quasi-theological writings for the highest and most notable expressions.” No one, in truth, will deny the accuracy of this claim for those ages before the Reformation transferred the centre of political authority from church to state. What is too rarely realised is the modernism of those writings in all save form. Just as the medieval state had to fight hard for relief from ecclesiastical trammels, so does its modern exclusiveness throw the burden of a kindred struggle upon its erstwhile rival. The church, intelligibly enough, is compelled to seek the protection of its liberties lest it become no more than the religious department of an otherwise secular society. The main problem, in fact, for the political theorist is still that which lies at the root of medieval conflict. What is the definition of sovereignty? Shall the nature and personality of those groups of which the state is so formidably one be regarded as in its gift to define? Can the state tolerate alongside itself churches which avow themselves societates perfectae, claiming exemption from its jurisdiction even when, as often enough, they traverse the field over which it ploughs? Is the state but one of many, or are those many but parts of itself, the one?