The sources for what we know of medieval thinking on law and nature include the Church Fathers and scholastic theologians, as well as Roman legal writings, and the somewhat confused cluster of texts that were drawn together in the twelfth and thirteenth centuries to constitute a body of recognized “canon law” for academic study. Of the first importance here is Gratian’s Decretum from the 1140s, the ground-breaking manual of canon law on which many subsequent treatises and commentaries would rely. These sources show how the classical understanding of a right (ius) as the subjective right of an individual contrasts with the characteristically medieval understanding of ius as “a system of objectively right relationships.” Medieval discussions of these issues pass through a complex set of questions about law and human nature, until the point where thinkers begin to stand away from tradition and ask radical questions. This leads through early modern political thought to a conventionalism that says morality is a mere convention that depends on the interaction between individuals.

DEFINITIONS AND CONCEPTS: ‘LAW’ AND ‘NATURE’

For the clusters of concepts for which we use the modern English words ‘law’ and ‘nature,’ a series of Latin terms were used from the ancient world to the Middle Ages, often equivocally, and with a shifting range of meanings.