The Trinitarian Theology of Saint Thomas Aquinas - El Camino ...

56 The Processions
procession of an interior reality, for the immanent action, and procession of an
external reality, for the transitive action. One must recognize two analogous
kinds of actions in God: the Trinitarian processions, in the one case, and the
actions of creation and government in the other.23
The example constantly used by St Thomas is that of the architect: the
immanent action takes place when the architect mentally conceives the plan of
the building which he is going to construct, and he wills its construction;
then, in the transitive action, the architect concretely realizes his plan by
getting the building constructed. The next step is that the transitive action, or
‘procession ad extra’, implies a diVerence between the agent and the reality
which proceeds from his action.24 If one applies this to the processions of the
divine persons, then ‘the persons who proceed from it will be external to
the divine nature’, just as the house is of a diVerent nature from the mind
of the architect who conceives and wills it.25 For Thomas, this is the trap into
which both Arianism and Sabellianism fall, in their own diVerent ways:
Some have understood this procession in the sense of an eVect proceeding from its
cause; so Arius took it, saying that the Son proceeds from the Father as the Wrst
amongst his creatures, and that the Holy Spirit proceeds from the Father and the Son
as the creature of both. But then, neither the Son nor the Holy Spirit would be true
God . . . Others take the procession to mean the cause proceeding to the eVect, as
moving it, or impressing its own likeness on it; in which sense it was understood by
Sabellius, who said that God the Father is called Son in assuming Xesh from the Virgin
Mary, and that the Father also is called Holy Spirit in sanctifying the rational creature
and moving it to life.26
By conceiving the generation of the Son as if it were a transitive action,
Arianism sets up an a priori interdiction against understanding the authentic
divinity of the Son and the Holy Spirit. Sabellianism does something analogous
from the opposite end of the spectrum: it allows one to maintain the
divinity of the Son and Holy Spirit but only by conXating them with
the Father, treating them as the modes through which the Father acts in the
world. It is no surprise that Arianism and Sabellianism both make the same
misjudgement. It is true that, in trying to avoid Sabellianism, Arius went for
the opposite mistake,27 but nevertheless the contraries meet on one point:
both connect the generation of the Son to an ‘external nature’,28 Arius relating
it to the production of a creature, and Sabellius to incarnation. Thus: ‘Careful
23 De potentia, q. 10, a. 1; SCG II, ch. 1 (no. 854).
24 ST I, q. 27, a. 1, ad 2. 25 De potentia, q.9,a.9. 26 ST I, q. 27, a. 1.
27 SCG IV, ch. 6 (no. 3387); De rationibus Wdei, ch. 9: ‘Arius, trying to avoid Sabellius’ error,
which conXated the persons of the holy Trinity, fell into the opposite error, dividing the essence
of the deity.’
28 SCG IV, ch. 7 (no. 3425).