Juridical concepts – specialized terms used in legal reasoning – have adaptive properties which allow for their coevolution with the social relations that they describe and constitute. Concepts form a bridge between empirical facts and legal norms. As such they allow data about the social world to enter legal discourse and frame normative judgments. Their defeasibility allows them to adjust to changes in their social and economic context. Studying juridical concepts in their historical context opens up new perspectives on institutional change and contributes to our understanding of social reality.