In Law and Revolution, law professor Harold Berman famously described how legal pluralism, a central feature of the Western legal tradition, traces back to the Middle Ages. And medieval legal pluralism was not simply a product of competing jurisdictions, but of a philosophy comfortable with complexity generally.
Here is an interesting-looking new book on medieval philosophy from Penguin Random House, The Wisdom of the Middle Ages, by Michael K. Kellogg. The publisher’s description follows:
This engaging survey of important works from late antiquity to the beginning of the Renaissance reveals the depth of thought and the diversity of expression that characterized the Middle Ages. Michael Kellogg demonstrates that medieval thought owes far more to ancient philosophy than is generally supposed; that poets of this era were as sophisticated and nuanced as their ancient counterparts; and that writers of this time anticipated most of the lines of inquiry that gave rise to the Renaissance.