One has to keep in mind that, in the doctrine of St Thomas, sanctifying grace involves the level of the essence or nature, which it elevates, while adoptive filiation, being a personal property, concerns the level of the act of being which is constitutive of ontological personality.* Speaking of cause and effect between the two levels requires precise use of metaphysical notions in the order of creation and even more in that of the supernatural elevation. To say that the Christian is "a son of God through or by grace" is not equivalent to saying that "adoptive filiation is an effect of the infusion of created grace." If one does not explain well this this last affirmation, it could appear that adoptive filiation is a juridical reality much like human adoption, when in fact it is a true participation in the subsistent Filiation which transforms the person into a son of God.
*"Supernatural divine filiation and sanctifying grace are inseparable but distinct realities: divine filiation is a 'personal property'." (St Thomas, Summa Theologiae q23 a4 c)
--Ernst Burkhart & Javier López, Vida cotidiana y santidad en la enseñanza de San JOsemaría. Estudio de teología espiritual. II. Madrid: Rialp, 2011 (--translation by jmo mandia)
Sanctifying grace affects the nature, divine filiation affects the person
