BEFORE DISCUSSING IDEOLOGY in the Carolingian period let us make a few basic assertions. First of all, between the eighth and early tenth centuries in the Frankish kingdom, any ideology that could be articulated was built upon Christian tradition, and this was the sole ideological tool capable of unifying the regional elites of the Empire. Accordingly, ideology would be presented in the terms of ecclesiology, as I will soon describe (that is, the theological doctrine of the Christian Church). And the Western Christian tradition drew on two main textual sources: Scripture and patristic writings, comprising texts written in Latin and Eastern Christian texts translated into Latin.

Secondly, a Carolingian ideology became a necessity for Carolingian rulers after the development of a large Christian state that covered much of Western Europe. For the first time since the dissolution of the Western Roman Empire, almost all Latin Christendom was contained in a single political structure. The Carolingian conquest took place in stages between Charles Martel and Charlemagne, and it ended with the victories of Louis the Pious. By the end of the ninth century, by inheritance or by his own wars of conquest, Charlemagne dominated a vast territory. This is a matter of Realpolitik, but once the conquest was over, it was necessary to provide a unifying ideology to all the subjected territory; it was necessary to move on from a kingdom built by conquest to an empire unified, and this was done via Christianity.

For some historians of Late Antiquity, as Robert Markus, the Christianization of Europe was a fait accompli by the end of that period. It is true that the European states of the sixth century—the famous Barbarian Kingdoms of traditional historiography—declared themselves Christian, and that Christianity was a varnish that covered these societies. But Christianized Europe, before and after the conversion of the last Arian Visigothic king Reccared in 589, was actually, as Peter Brown pointed out, a sum of micro-Christianities. They were very loosely united by the same Nicene–Constantinopolitan creed, they had distinctive pious, liturgical, and calendrical practices, and in some cases they even included syncretic pagan beliefs. Brown believes that the Carolingian conquest put an end to this Christianity of Late Antiquity and gave birth to something new: medieval Christianity.