The Sixth Ecumenical Council on Free Will

Constantinople III, Sixth Ecumenical Council 680-681

For should we say that the human nature of our Lord is without will and operation, how could we affirm in safety the perfect humanity? For nothing else constitutes the integrity of human nature except the essential will, through which the strength of free-will is marked in us; and this is also the case with the substantial operation. For how shall we call Him perfect in humanity if He in no wise suffered and acted as a man? For like as the union of two natures preserves for us one subsistence without confusion and without division; so this one subsistence, showing itself in two natures, demonstrates as its own what things belong to each. (Prosphneticus to the Emperor)