Against the Church of Rome, however, there was directed the affirmation that the Holy Ghost proceeds from the Father and not from both Father and Son; this rejection of the filioque was not unwelcome to the Turks.
He had considerable knowledge of theology, took a prominent part in the theological controversies of the time, and was responsible for the addition of the clause filioque to the Nicene Creed.
The first session at Florence and the seventeenth of the union council took place on the 26th of February 1439; there ensued long debates and negotiations on the filioque, in which Markos Eugenikos, archbishop of Ephesus, spoke for the irreconcilables; but the Greeks under the leadership of Bessarion, archbishop of Nicaea, and Isidor, metropolitan of Kiev, at length made a declaration on the filioque (4th of June), to which all save Markos Eugenikos subscribed.
The decree explains the filioque in a manner acceptable to the Greeks, but does not require them to insert the term in their symbol; it demands that celebrants follow the custom of their own church as to the employment of leavened or unleavened bread in the Eucharist.
The decree for the Armenians was published on the 2 2nd of November 1 439; they accepted the filioque and the Athanasian creed, rejected Monophysitism and Monothelitism, agreed to the developed scholastic doctrine concerning the seven sacraments, and conformed their calendar to the Western in certain points.