“For Thomas [(as distinguished from Richard of St. Victor, Bonaventure, etc.)], innascibility, being strictly negative, is a secondary property [(proprietas)]; it comes in solely to qualify the paternity of God[, which is primary]. Indeed, negation can express the dignitas characteristic of a property only in virtue of the affirmation on which it is founded. It is thus that innascibility presupposes paternity. To be sure, innascibility can seem more perfect than paternity, inasmuch as innascibility is utterly incommunicable, whereas paternity is in fact communicated to creatures. But if one attends to it, innascibility manifests in reality the incommunicable character of the divine paternity itself: the divine paternity is utterly unique and transcendent; only God the Father is therefore totally and uniquely Father, without having ever been [a] son--as Hilary, following Athanasius, had stressed so eloquently. Innascibility expresses with great simplicity the incommunicability of the divine paternity.
“In its strictly negative sense, innascibility exercises, therefore, a corrective function with respect to all erroneous projection of human paternity onto God.”
Fr. Emmanuel Durand, O.P., “Le Père en sa relation constitutive au Fils selon saint Thomas d’Aquin.” Revue thomiste 107, no. 1 (2007): 69 (47-72). A difficult article, which I can't yet say I've mastered. Cf. http://liberlocorumcommunium.blogspot.com/2009/11/calling-fathers-father.html.