This paper will concentrate on the mystical foundation of the political order as it can be found in Nicholas of Cusa's early work, De concordantia catholica, written between 1431 and 1435 during the Council of Basel, the last general council before the Reformation. At the heart of the council debate was the authority in the Church, i.e. the main point of reference for concordance and unity within the church. De concordantia catholica is a work of great importance for understanding the Catholic tradition at the threshold of modernity, and for understanding current developments in the Church. The real innovation of the book is Cusa's understanding that, although the social order is founded in an immutable God, the institutional and legal mediators of this order are entities within history, and therefore changing and changeable. Cusa proposes a pragmatic realism in De concordantia catholica, which could equally be called 'mystical', as he focuses his reflections on the hidden unity of the mystical body of the church. The book, therefore, is of crucial importance for the development of Catholic ecclesiology. The mystical character of political agreement is no longer situated in a vertical, hierarchical foundation, as was the case in the Dionysian model. Cusa's new conjectural method shows that the inability to provide a legal, philosophical, or theological base for political agreement is paramount. The agreement itself is a mystery, and it is this mystery that forms the very foundation of the Church; a mystery, not to be localized in God or the subject, but in the dynamics of a social network, a space of trust and love in which the mystery of agreement can manifest itself.