The doctrine of national or popular sovereignty was no new conception for the French nation. It had been appealed to by the Church to check the secular power, and by the Empire to check ecclesiastical encroachments. Thomas Aquinas, the oracle of the Church, had recognized the popular will as a limitation upon the royal power, and had commended the elective form of monarchy.[44] Marsilio of Padua, in his _Defensor Pacis_, was even more pronounced in favor of popular sovereignty. “The sovereignty of the State,” he said, “rests with the people; by it properly are the laws made and to it they owe their validity. From the nation itself proceeds all rights and powers, it is the authoritative lawgiver among men.”[45] In the sixteenth century the Calvinists and the League alternately made use of the theory of popular sovereignty.[46] This theory was revived in the eighteenth century and popularized by Rousseau and his disciples. The doctrine of natural rights has not so remote an origin for France. De Tocqueville rightly pointed out the distinction between liberty, regarded as “the enjoyment of a privilege” and liberty considered as “the exercise of a universal right”; he also showed that the Romans and the feudal aristocracy figured their liberties to themselves under the former type; and that it was not till the eighteenth century that the French nation began to conceive of liberty as a natural right.[47] This transformation of the theory of liberty from a privilege to a natural right was chiefly accomplished after 1734. Boulainvilliers, in _L’Histoire de l’ancien gouvernement de la France_, published (1727) in Holland after his death, asserted as its fundamental thought: “Le gouvernement féodal est le chef d’oeuvre de l’ésprit humain.” To the author, all progress of royal, civil, or municipal authority is an usurpation of the rights of the nobility, who were the only heirs of the early Franks, conquerors of the Gauls.[48] This champion of the feudal aristocracy was not answered in the name of democracy, but of privileged rights. Abbé Dubois, the secretary of the French Academy, replied in “the name of Roman Gaul, semi-municipal and semi-monarchical.” This reply, entitled, “_Histoire critique de l’établissement de la monarchie française_” (1734), denied the Frankish conquest and asserted that the French monarchy had succeeded in a peaceable way to the rights of the Roman Empire over the Gauls, and that the feudal system had been established by usurpation several centuries later. Public opinion and the judgment of the _savants_, says Martin, pronounced in favor of Dubois.[49]