Chapter 56 — That it is impossible for there to be more than three persons in God

There cannot be more than three persons in God, for the divine persons cannot be multiplied by a division of their substance, but solely by the relation of some procession; and not by any sort of procession, but only by such as does not have its term in something outside of God. If the relation had something external as its term, this would not possess the divine nature, and so could not be a divine person or hypostasis. But procession in God that does not terminate outside of God must be either according to the operation of the intellect, whereby the Word proceeds, or according to the operation of the will, whereby love proceeds, as is clear from the things said. Therefore, no divine person can proceed unless he proceeds as the Word, whom we call the Son, or as love, whom we call the Holy Spirit.

Moreover, since God comprehends everything in his intellect by a single gaze, and similarly loves everything by a single act of his will, there cannot be several words or several loves in God. If, then, the Son proceeds as Word, and if the Holy Spirit proceeds as love, there cannot be several Sons or several Holy Spirits in God.

Again, the perfect is that beyond which there is nothing. Hence a being that tolerates anything of its own kind outside itself is not absolutely perfect. This is why things that are simply perfect in their natures are not numerically multiplied, such as God, the sun, the moon, and so on. But both the Son and the Holy Spirit must be simply perfect, since each of them is God, as we have shown. Therefore, several Sons or several Holy Spirits are impossible.

Besides, that by which a subsistent thing is this particular thing (distinct from other things) cannot be numerically multiplied, because an individual cannot be predicated of many. But it is by sonship that the Son is this divine person, subsisting in himself and distinct from the other divine persons, just as Socrates is constituted as this human person by individuating principles. Accordingly, as the individuating principles whereby Socrates is this man cannot pertain to more than one man, so sonship in the Godhead cannot pertain to more than one divine person. And it is similar with the relation of the Father and the Holy Spirit. Hence there cannot be several Fathers in God or several Sons or several Holy Spirits.

Further, things that are one according to form are not numerically multiplied except through matter; thus whiteness is multiplied by existing in many subjects. But there is no matter in God. Consequently, whatever is one in species and form in the Godhead cannot be numerically multiplied. Such are paternity and filiation and the procession of the Holy Spirit. And thus there cannot be several Fathers or Sons or Holy Spirits in God.