It was not the Treaty of Cateau-Cambrésis in 1559 that ended the Valois-Habsburg struggle, but rather the Peace of Augsburg four years earlier, which set the constitutional terms of the new society of states that emerged from this epochal war. Charles V's campaign for a single Christendom foundered not so much on French victories as on the advent and growing strength of the new princely states.
Indeed at first sight, the phenomenon appears to be universal in Europe. One finds it spreading to Scandinavia, where the Reformation provided Danish and Swedish kings with the means of establishing strong rule; even in Russia, Ivan III and Ivan IV seem almost to duplicate the work of England's Henry VII and Henry VIII, of France's Louis XI and Francis I.4
What is sometimes less appreciated is that the principle that was the basis of Augsburg—the famous cuius regio eius religio—transformed this multilateral treaty into a constitution for the new society of princely states. This principle may be roughly translated as “he who rules, his is the religion”; it provides that the religion of a state is determined by the choice of the sovereign, with free immigration to all his subjects. It was an imaginative concept, although it had its roots in the prior practices of princes attempting to keep outside interference from complicating their relations with their subjects. Most significantly, cuius regio eius religio implied a “theory of sovereignty by the states of Europe that permitted no distinction in law between a Catholic and a Protestant country.”5 Thus the basis for a comprehensive society of states was formed.
The defeat of the Habsburg bid for empire6 had destroyed Charles's hopes for a Respublica Christiana; the Peace of Augsburg ratified this failure and introduced instead the notion of individual state supremacy. Implicit in the principle of cuius regio eius religio is the territorial delimiting of sovereignty and the notion of state supremacy within that sovereignty. “There was thenceforth [after the Peace of Augsburg] to be no lord of the world, imperial or otherwise, for the simple reason that there was no single world. There were England, France, and Spain. The life of each was to be centralized within its ultimate sovereign.”7
Medieval Christendom had known no society of politically distinct states.8 After princely states first appeared in Italy, 9 they gradually spread throughout Europe, replacing the universal, overlapping structures of ecclesiastical, feudal society10 with a discrete, territorial pattern of states. Latin, once learned by everyone in the learned classes, was replaced as the bureaucratic language of officials by increasingly standardized vernaculars. Adam Watson has observed that although at the time of the Peace of Augsburg, “the principle of cuius regio eius religio applied formally only to the Holy Roman Empire,… the practice quickly extended throughout the Christian commonwealth of Europe. It carried, as a corollary, another principle which rulers readily acknowledged and proclaimed though they did not always scrupulously observe it: non-interference by one state in the affairs of another.”11
This doctrine of the essential separateness of the new states into which Christendom was now divided was indeed the result of the principle of Augsburg. This principle, which enshrined the legitimacy of state sovereignty, and denied the universal order of the Respublica Christiana, replaced that order with the society of princely states whose horizontal relationship indicated their mutual sovereignty. Thus the principle of Augsburg not only excluded the imperial state sought by Charles, but gave a constitutional foundation to the society of princely states.12