St. Thomas’ life extended over the crest of feudal civilization. This term suggests the idea of a particular type of warrior society, namely, of a society dominated by a warrior stratum that was organized, on the principle of vassalage, in a hierarchy of fief-endowed lords and knights. From the standpoint of this hierarchy of warriors, the old distinction between men of free status and men of unfree status had lost much of its original significance. What mattered was not whether a man was free or not, but whether he was a knight or not. Even the Emperor of the Holy Roman Empire of German Nationality—to use the official phrase—who was in theory recognized as the feudal overlord of all Christianity, primarily was, and felt himself to be, a knight; and even the unfree man was a knight as soon as he had got hold of a horse and arms and had learned how to use them—which was at first a very simple matter, though in St. Thomas’ age it had become a highly skilled occupation. This warrior class enjoyed unrivaled power and prestige, and hence impressed the stamp of its own cultural pattern upon the civilization of feudal times.

The economic base of this social pyramid consisted of the dependent peasants and manorial craftsmen on whose work the warriors lived. We thus seem to behold what at first sight looks like a structural unit in the sense that the phrase Social Pyramid is indeed meant to convey. But this picture is quite unrealistic. Societies, with the possible exception of primitive tribes and full-fledged socialism, are never structural units, and half the problems they present arise from the fact that they are not. The society of feudal times cannot be described in terms of knights and peasants any more than the society of capitalist times can be described in terms of capitalists and proletarians. Roman industry, commerce, and finance had not been destroyed everywhere. Even where they had been destroyed or where they had never existed, they—and consequently classes of bourgeois character—had developed or developed again before St. Thomas’ day. In many places these classes had outgrown the framework of the feudal organization and, helped by the fact that a well-fortified town was normally impregnable to the knights’ arts of warfare, they had successfully challenged the rule of the feudal lords— the most conspicuous instance being the victorious resistance of the towns of Lombardy. As a historical reality, therefore, feudalism means the symbiosis of two essentially different and largely, though not wholly, antagonistic social systems.