Sovereignty—suprema potestas—in the later Middle Ages was not blessed with Austinian simplicity: it was a complex and contradictory thing. Held by the ecclesiastical and lay powers, held by pope, emperor, king, and city-state, few populi were subjected to one authority alone. Not only did there exist a hierarchy of sovereign powers in the Western community, de iure and de facto, but the suprema potestas was in itself limited. It was the extent of this limitation and the degree of sovereignty possessed by the various governments which exercised, to a very large extent, the minds of later medieval and Renaissance jurists. A major reordering of the relationship between the spiritual and secular authorities was occasioned with the propounding of the via media by Thomas Aquinas in the thirteenth century. Thomistic doctrine did much to promote and enhance the importance of civil government at the expense of hierocratic theories, but, as Michael Wilks observes in his fundamental study of medieval sovereignty, it proved to be almost as dangerous to the concept of the societas humana as to that of the societas christiana. Quite simply, as long as moral standards were applied to earthly government, political evaluation was forced into the theological sphere, and so, to some degree, into the realm of papal determination. And to Thomistic influences, as Michael Wilks again remarks, the civilians nearly all succumbed. Laying their claims very largely upon the bases of Roman law and Aristotle, legists expounded a profoundly secular philosophy; but the seemingly logical conclusion—logical, that is, to the modern mind—that secular man was freed from the theological order was not reached. The pope retained both a unique degree of dignitas and a superior degree of authority; he was head of the populus christiana, and this awesome position bestowed upon him certain ultimate rights and responsibilities in the affairs of secular corpora, even though these corpora were sovereign entities. In other words, papal sovereignty, although increasingly restricted and relegated to the realm of theory as the early modern State evolved, none the less remained a potent force; indeed, as it will be seen, in a particular aspect it fulfilled for the jurist a critical need of the young State.