Invited to Constantinople in the 1160’ies by the emperor Manuel I Komnenos to present the Western view on the Trinity in the so-called Demetrius of Lampe affair, the Italian theologian and diplomat Hugo Eterianus took part in the dogmatic discussions on the relation between the Father and the Son. Afterwards Hugo composed De sancto et immortali Deo to present the dogmatics of the Western church in both Greek and Latin, and sent the opus to pope Alexander in Rome and to the patriarch in Antioch. The accompanying letters and well as the treatise itself contain a number of attacks on the Greek theologians of the Byzantine period.