r his scholastic philosophy ever did. Critical to the revival of the West was the conversion of the fierce Scandinavian and Slavic barbarians to Christianity. No civilization was possible until this happened. Also critical was the church’s role as a unifying force. Governments in the Middle Ages were weak. Internecine warfare was tearing society apart. What was needed was a unifying force to keep infighting to a minimum. The church, by making use of crusades against Islam, managed to direct the energies of the warlike barons that ruled Europe against foreign targets, instead of against each other (and against the emerging merchant cities).
Whatever role ideas played in the course of European history, their affect is always greatly influenced by the development of institutions that are not the product of human design. Capitalism is not caused by the application of philosophical, political, or economic ideas. The Middle Ages were not economically or politically sophisticated enough to understand the workings of a complex free market, or to develop them a theory that would allow them to create a capitalist system. Such an understanding would only begin to develop in the 18th century. As a matter of fact, the nascent capitalism of the Middle Ages had to develop in the teeth of several ideas that went against its fundamental grain, such as notions concerning rank and birth, the honor codes of the feudal barons, and deep-rooted prejudices against usury (prejudices, I might add, shared by Aquinas and his philosophical idol, Aristotle).