This study aims to highlight two milestones of the complex progressive process within the sovereign power from the Christian Middle Ages: First, the beginning of the fourteenth century, where the prior clear signs of a split in sovereignty within the doctrine of sacerdotalism appear. The second one, at the end of the sixteenth century, where the legal factor is accentuated and it accelerates the process of secularization dividing the powers of Church and State to the point of accepting the doctrine of popular sovereignty. In my view, the process concerns the issue of relations between the sovereign power of the Church and the State, just before Jean Bodin and others formulate a theory of sovereign authority, that is, before the birth of the Modern State.