7 For as to those whose soul and heart were one, I ask whether they were one through faith in God? Yes, assuredly, through faith, for through this the soul and heart of all were one. Again I ask, is the faith one or is there a second faith? One undoubtedly, and that on the authority of the Apostle himself, who proclaims one faith even as one Lord, and one baptism, and one hope, and one God. If then it is through faith, that is, through the nature of one faith, that all are one, how is it that thou dost not understand a natural unity in the case of those who through the nature of one faith are one?
For all were born again to innocence, to immortality, to the knowledge of God, to the faith of hope. And if these things cannot differ within themselves because there is both one hope and one God, as also there is one Lord and one baptism of regeneration; if these things are one rather by agreement than by nature, ascribe a unity of will to those also who have been born again into them. If, however, they have been begotten again into the nature of one life and eternity, then, inasmuch as their soul and heart are one, the unity of will fails to account for their case who are one by regeneration into the same nature.
Source: On the Trinity (New Advent)