For some decades now, reasonable disagreement has been a hot topic in (analytic) philosophy. People eagerly dispute the justification with which reasonable persons can uphold contrary beliefs or opinions once they realize that other reasonable persons oppose their views. Less attention is paid to the history of conceptualizations and regulations of reasonable disagreement. It is widely believed that preoccupation with the moral and epistemological underpinnings of disagreement between reasonable peers is a very recent phenomenon. The present inquiry shows that this belief seriously misrepresents European intellectual history. Since at least the thirteenth century, disagreement between scholastic specialists has been accepted as a fact not to be eliminated but managed by discursive rules that allowed for upholding controversial positions. As argued here, the development of the political, juridical, economic, and moral governance of medieval Christianity crucially depended on the rules and entitlements that flexibly regulated reasonable disagreement between academic ‘specialists’ who assessed right doctrine and right conduct in these fields. However, the extensive theoretical analysis of reasonable disagreement's moral and epistemological underpinnings had to wait until the seventeenth century, when new scholastic doctrines sparked a huge debate on the nature and assertability of probable opinions. This debate produced the most detailed investigation of the foundations of reasonable disagreement before the twenty-first century.

The first section of this chapter briefly introduces the concept of reasonable disagreement and underlines the importance of its historical dimension.