*Thesis III: Sanctifying grace is lost by mortal sin.*
This thesis also embodies an article of faith.
Proof. Calvin asserted that neither justification nor faith can be lost by those who are predestined to salvation, and that the unpredestined are never truly justified. Luther held that justifying grace is lost solely through the sin of infidelity. Against the former the Council of Trent declared: “If anyone saith that a man once justified can sin no more, nor lose grace, and that therefore he that falls and sins was never truly justified; ... let him be anathema.”(1203) Against the latter the same council defined: “If anyone saith that there is no mortal sin but that of infidelity, or that grace once received is not lost by any other sin, however grievous and enormous, save by that of infidelity, let him be anathema.”(1204) At the same time, however, the Holy Synod expressly declared that venial sin does not destroy the state of grace: “For although during this mortal life, men, how holy and just soever, at times fall into at least light and daily sins, which are also called venial, they do not therefore cease to be just.”(1205)
a) This teaching is so obviously in accord with Sacred Scripture that we confine ourselves to quoting three or four passages. Ezechiel says that sanctifying grace may be irretrievably lost: “If the just man turn himself away from his justice, and do iniquity according to all the abominations which the wicked man useth to work, shall he live? All his justices which he hath done shall not be remembered; in the prevarication, by which he hath prevaricated, and in his sin, which he hath committed, in them he shall die.”(1206) Our Lord Himself admonishes His Apostles: “Watch ye and pray, that ye enter not into temptation.”(1207) St. Paul not only warns the faithful in general terms: “He that thinketh himself to stand, let him take heed lest he fall;”(1208) but expressly designates certain mortal sins as a bar to Heaven: “Neither fornicators, nor idolaters, nor adulterers, nor the effeminate, nor liers with mankind, nor thieves, nor covetous, nor drunkards, nor railers, nor extortioners, shall possess the kingdom of God.”(1209)
b) The teaching of Tradition was brought out clearly in the fight against Jovinian.