a) The Tridentine Fathers base their teaching on a number of Scriptural texts which either expressly declare or presuppose that grace is capable of being increased in the soul after justification.
Thus we read in Prov. IV, 18: “The path of the just, as a shining light, goeth forwards and increaseth even to perfect day.”(1179) Ecclus. XVIII, 22: “Let nothing hinder thee from praying always, and be not afraid to be justified even to death: for the reward of God continueth for ever.”(1180) 2 Pet. III, 18: “Grow in grace and in the knowledge of our Lord and Saviour Jesus Christ.”(1181) 2 Cor. IX, 10: “[God] will increase the growth of the fruits of your justice.”(1182) Eph. IV, 7: “But to every one of us is given grace, according to the measure of the giving of Christ.”(1183) Apoc. XXII, 11 sq.: “He that is just, let him be justified still; and he that is holy, let him be sanctified still. Behold, I come quickly, and my reward is with me, to render to every man according to his works.”(1184)
b) Tradition found definite utterance as early as the fourth century.
When Jovinian attempted to revive the Stoic theory of the absolute equality of all virtues and vices, he met with strenuous opposition on the part of St. Jerome, who wrote a special treatise _Contra Iovinianum_, in which he said: “Each of us receives grace according to the measure of the grace of Christ (Eph. IV, 7); not as if the measure of Christ were unequal, but so much of His grace is infused into us as we are capable of receiving.”(1185) St. Augustine teaches that the just are as unequal as the sinners. “The saints are clad with justice (Job XXIX, 14), some more, some less; and no one on this earth lives without sin, some more, some less: but the best is he who has least.”(1186) But, we are told, life as such is not capable of being increased; how then can there be an increase of spiritual life? St. Thomas answers this objection as follows: “The natural life pertains to the substance of man, and therefore can be neither augmented nor diminished; but in the life of grace man participates _accidentaliter_, and consequently he can possess it in a larger or smaller degree.”(1187)
c) From what we have said it is easy to understand the distinction which theologians make between justification as _gratia prima_ and justification as _gratia secunda_. The latter is merely another term for an increase of grace after justification.