Gregory of Nyssa: "[...]it is impossible that those realities that are separated from each other by natural principle coincide with one another in the form of activities[...]"

"Therefore, if we see that the activities (ἐνεργείας) performed by the (ἐνεργουμένας παρα) Father, by the Son and by the Holy Spirit differ one from another, based in the diversity of activities, we conjecture that also the natures that perform them are diverse. In fact, it is impossible that those realities that are separated from each other by natural principle (κατά τον τῆς φύσεως λογον) coincide with one another in the form of activities (fire does not produce cold, nor ice heat), but according to the differences of natures the activities [performed] by them are also separated one from another. Instead, if we conceive as unique the activity of the Father, the Son and of the Holy Spirit, [an activity] which is not distinguished nor changed in any of them, then it is necessary to infer the unity of nature from the identity of activity." (Ad Eustathium, GNO III/1, 11, 3-15, tr. Maspero, 2007, p. 57)