In Liber apologeticus Eunomius of Cyzicus discuses the generation of the Son as the action of Father’s will. The Anti-Arian writers argued that this process did not effect in Son having a different essence than the Father. The core of this notion is to show the difference between the two phases of procession in Father’s intellect and will. While the action of intellect would produce another essence (ousia), the action of will does not.
Such a conclusion points to the Enneads by Plotinus and his notion of the One who “wills itself as being creative”. The first act of will happens internally and remains in the One itself, but the second one leads out to production of a lower reality of the Intellect. In the case of Eunomius, the matter is especially interesting because his opinion on internal procession of the will could be seen as a rejection of relying on Greek philosophy in resolving the problems of the Christian Faith.
The problem is whether we could really ascribe the Plotinian influence to the adversaries of Eunomius. Torstein Theodor Tollefsen suggested that the Plotinian doctrine of divine activity could indeed be seen there. However, in order to fully understand this problem it is necessary to trace it back to the Aristotelian theory of the movement in substances which can move by themselves (kat’ auto) and to analyze how this concept was exploited by Plotinus.