When he finally acquired a career as a cleric, he took an active part in the theological controversies between the Eastern Orthodox Church and the Roman Catholic Church, writing treatises on the Procession of the Holy Spirit, advocating the western usage.
Cando finalmente adquiriu unha carreira como clérigo, tomou parte activa nas controversias teolóxicas entre a Igrexa Ortodoxa Oriental e a Igrexa católica, escribindo tratados sobre a Procesión do Espírito Santo, avogando polo uso occidental.