In the fight against adoptionism, Charlemagne benefited from the precious aid of Alcuin. This Anglo-Saxon theologian and pedagogue (v. 735-804) exerted great cultural and religious influence on the Emperor and his entourage: his actions and his oeuvre – including a voluminous correspondence – made of him one of the lynchpins of what has been called the ‘Carolingian Renaissance.’ In strictly speaking religious terms, Alcuin, who had retired to the Saint-Martin de Tours Abbey – of which he was the Abbot – in 796, threw all his energy into the advent of an ideal Christian Empire, the very same whose broad outlines had been sketched in the capitulary legislation of March 23, 789, Admonitio generalis (General Admonition). To this end it was necessary to eradicate the adoptionist ‘heresy’, a ‘major obstacle in the path of a Frankish people marching towards salvation.’ He was convinced that there could only exist a single accepted meaning of the Evangelical message, loyal to the Patristic heritage. That is why the theologian, who was against the use of arms in the propagation of the ‘true’ faith and thus an opponent of the forced conversion of the Saxons, launched new preaching campaigns in Francia, carried out in the name of the indivisible Trinity. This manner of proceeding, compared with the Holy War, bore fruit amongst the Avars, an evangelisation success which inspired Alcuin to state: ‘if the Saxons have renounced the sacrament of baptism so many times, it is because the fundamentals of faith have never taken root in their hearts.’ 

In the final part of her book, which carries the significant title ‘Preaching the Trinity in the Carolingian Kingdom,’ Florence Close gets down to the task of seeing how Charlemagne tackled head on the vast project of cultural and religious reform, conceived in decisive manner by Alcuinian thinking, a project with obvious political underpinnings, as it consisted of working towards the unification of the Empire. In this respect he carried on the work undertaken by his father, Pippin III, who, strengthened by the Unction received from the hands of the Pope, had already attended to reforming the Frankish Church on the Roman model. He, nevertheless, and particularly from the last decade of the 8th century onwards, had an intimate conviction, in other words one in which he was on a divine mission which pushed him not only to convert the pagans and bring back into the fold the adoptionists and other heretics, but also, the ultimate goal, uniting all the Christians within a single area – the Imperium christianum – thanks to a shared belief in the Trinity. The credo which bears his name, written by Alcuin and dating from 794, in particularly served this end: it was to be the reference for the court theologians and the norm in terms of dogma for Western Christianity.

Backed up by an impressive mass of sources – narrative, diplomatic, epistolary, legislative, theological and Patristic –, and also leaning on the most recent key historical works,  this remarkable study has made of its author the winner of the 2009 Royal Academy of Belgium (Class of Letters) competition. A recognition which gives her conclusion all the more weight: ‘Quite evidently, Charlemagne counted belief in a single God in three persons amongst the number of pillars on the basis of which he intended to unify his kingdoms into a single Empire. Wasn’t believing in the Trinity the same as believing in the diversity in Unity? [...] The programme of religious reform and the expansion of Christian doctrine and culture contributed to the general strategy of Carolingian government.’