On The Holy Trinity by St. Augustine
Chapter 4.--The Trinity and the Image of God is in that Part of the Mind Alone Which Belongs to the Contemplation of Eternal Things.
4. When, therefore, we discuss the nature of the human mind, we discuss a single subject, and do not double it into those two which I have mentioned, except in respect to its functions. Therefore, when we seek the trinity in the mind, we seek it in the whole mind, without separating the action of the reason in things temporal from the contemplation of things eternal, so as to have further to seek some third thing, by which a trinity may be completed. But this trinity must needs be so discovered in the whole nature of the mind, as that even if action upon temporal things were to be withdrawn, for which work that help is necessary, with a view to which some part of the mind is diverted in order to deal with these inferior things, yet a trinity would still be found in the one mind that is no where parted off; and that when this distribution has been already made, not only a trinity may be found, but also an image of God, in that alone which belongs to the contemplation of eternal things; while in that other which is diverted from it in the dealing with temporal things, although there may be a trinity, yet there cannot be found an image of God.