Cap. 6 Arg. 8: Saving grace of Christ—supernatural gifts; non-infallible media called grace
So by "grace of Christ" or saving grace, in Scripture's sense, we mean only those supernatural benefits and gifts aimed straight at salvation in Christ and eternal life. They fall into two ranks. Some are ordered to salvation through Christ, but not infallibly: Gospel preaching, illumination of minds in the mysteries of the faith—in short, whatever supernatural help tends to join people to Christ and set them in a state of salvation, yet has not actually joined them or moved them from death into life. The Apostle himself calls that preaching and knowledge of the Gospel "grace" (1 Cor. 1:4; 2:11). That is why 1 Peter 4:10 names preachers stewards of God's manifold grace. Augustine calls the Gospel itself Christian grace; Prosper calls it the Savior's grace—and in that sense says some nations live outside God's grace when no one there preaches Christ to them.
Latin
Nomine igitur gratiae Christi sive gratiae salutiferae, ex sensu Scripturarum acceptae, significantur solummodo ea beneficia ac dona supernaturalia quae directe ordinantur ad salutem in Christo et vitam aeternam obtinendam. Haec autem sunt in duplici discrimine constituta. Quaedam eorum sunt quae habent ordinationem ad salutem per Christum obtinendam, sed non infallibilem: qualia sunt Evangelii praedicatio, Illuminatio humanarum mentium in mysteriis fidei, et uno verbo, quicquid supernaturale eo tendit ut homines Christo conjungat et in statu salutis ponat, nondum tamen conjunxit, aut ex statu mortis in statum salutis transtulit. Hanc ipsam praedicationem et cognitionem Evangelii Apostolus gratiae nomine indigitavit, 1 Cor. i. 4. et ii. 11. Atque hinc est quod 1 Petr. iv. 10. vocat praedicatores Dispensatores ποικίλης χάριτος Θεοῦ. Sic Augustinus vocat ipsum Evangelium gratiam Christianam, De pecc. mer. et rem. l. 1. 22. Prosper vocat gratiam Salvatoris, De voc. Gent. l. 2. c. 17. (Et hoc sensu affirmat aliquas gentes extra gratiam Dei degere, quando scilicet ibi degunt, ubi nemo illis Christi Evangelium praedicat, Sentent. 10. super Capit. Gallor.)