Given the ongoing scholarly debates about the relationship between Eastern and Western versions of Trinitarianism, I found this quote from Thomas Aquinas interesting:
It is the custom with the Greeks to say that the Son and the Holy Ghost are principled [that is, that the Son and the Spirit proceed from the Father as their principle or cause]. This is not, however, the custom with our [Latin] Doctors because, although we attribute to the Father something of authority by reason of His being the principle, still we do not attribute any kind of subjection or inferiority to the Son or to the Holy Ghost, to avoid any occasion of error. In this way, Hilary says (De Trin. ix): “By authority of the Giver, the Father is the greater; nevertheless the Son is not less to Whom oneness of being is given” (ST, 1.33.1).
A couple of things stand out to me. First, Thomas recognizes the importance of carefully parsing the distinct terms used across the linguistic divide and the differing contexts that inform their meaning. Earlier in the article cited above, Thomas notes that the Greek-speaking theologians are comfortable using the term “cause” (Latin, causa; would the Greek be aitia?) with reference to the Father’s place in the Godhead but that those in the Latin-speaking West prefer “principle” (principium) since it is a “wider term” that avoids confusion. He does not quite argue that the two traditions are saying precisely the same thing with reference to the Trinity; he clearly prefers the clarity of the Latin terminology. But he makes an argument for this preference from semantic and contextual implications rather than from any fundamental point of disagreement.
Second, Thomas’s words also have relevance for debates about subordinationism. Thomas admits that the Father has a kind of “authority” (auctoritatis) as the principle of the Son and the Spirit in their eternal relations of origin. But this authority in no way implies subjection (subiectionem) or inferiority (minorationem). As the Hilary citation indicates, the Father is “greater” in terms of the eternal processions, but the persons proceeding are not lesser than the one from whom they proceed.