Some have said that talk of ‘substance’ metaphysics is erroneous, I’ll do a post on who in the days to come. Until then I think the following is instructive towards understanding, theologically, what substance metaphysics is referring to when the locus is grace. It is unfortunate when grace is depersonalized, because insofar as God in his being in becoming is grace, if this ontology of grace is applied to God we end up with a monad and not a personal God who is Triune.
As of late I’ve been talking with a few folks about Grace, and what Thomas Aquinas thought of it, and how he defined it using Aristotle’s categories of substance and qualities. Below I’m going to give a definition from a Latin theological dictionary on created grace or habitual grace.
habitus gratiae: habit or disposition of grace; a divine gift infused into the soul in such a way as to become a part of human nature. The habitus gratiae can therefore also be called gratia creata, created grace, as distinct from the uncreated power of God that brings it into existence, gratia increata. In addition, according to its function, the habitus gratiae can be called justifying grace (gratia iustificans) or sanctifying grace (gratia sanctificans). This concept, together with a related concept of an infused righteousness (iustitia infusa, q.v.), was rejected by the Reformers in so far as it cannot be correlated with the doctrine of a forensic justification (iustificatio,q.v.) on the ground of the alien righteousness (iustitia aliena) of Christ imputed to believers by grace alone through faith. The habitus gratiae implies an intrinsic righteousness to the believer, whereas the Reformer’s concept of imputed righteousness is extrinsic. Righteousness is viewed by the reformers and the Orthodox as inherent, or intrinsic …, in relation to the work of the Spirit in sanctification (sanctificatio,q.v.), but the concept, here, is expressed in terms of cleansing (renavatio, q.v.) rather than in terms of an infused disposition or habit. [Richard Muller, Dictionary of Latin and Greek Theological Terms: Drawn Principally from Protestant Scholastic Theology, 134]
In other words, created grace, for the Protestant, is incommensurate with the concept of grace as foreign and external mediated by the righteousness of Christ;and applied by the Holy Spirit. For Roman Catholics, historically as noted above, grace becomes part of the person, in the accidents, which is intrinsic to the person. The implication is that grace is something that can be manipulated by the person, depending on their particular disposition — this typically has been known as semi Pelagianism.