Originally the Councils of Toledo in ancient and early Medieval Spain administered internal ecclesiastic matters, issued important liturgical regulations, and settled differences between various doctrinal interpretations like Priscillianism and Arianism. After the collapse of the Roman Empire and the conquest of the Iberian Peninsula by the Visigoths in the late 5th century they profoundly changed their institutional architecture in structural and functional terms. Henceforth the Toledanum played a decisive role in the quarrels between the Visigothic kingship and nobility. It evolved from an ecclesiastic institution into a national council that executed the legislative process, affirmed the power of kingship, disciplined the king’s noble opponents, and provided a socially integrative instrument that stabilized the ethnically heterogeneous Visigothic realm. This paper examines the institutional change of this early ecclesiastic representative body on the basis of Evolutionary Institutionalism. It highlights the internal and external selection criteria that led to the mentioned evolutionary changes and illustrates that Evolutionary Institutionalism provides a useful theoretical framework to analyse institutional change over time
