Summa summae S. Thomae, Tomus II

I say : Justified man can truly and properly merit something from God, even eternal life itself.

This is of faith, decided in various councils: Arausican II, can. 18 ; Lateranense IV, under Innocent III, cap. Firmiter ; and lastly in Trid., session VI, cap. 16 and can. 32, against the Lutherans and Calvinists, who, since they contend that all works are evil, acknowledge in him no work that is meritorious at least of eternal life.

It is proved 1°. By merit we understand nothing else than a good work compared to a reward. Now Scripture everywhere proposes to us eternal life as to be rendered to the good works of the just. Therefore. — Proof of the minor. Matth., V, 12, it is said : Rejoice and exult, because your reward is great in heaven. Ibid., cap. XIX, 27-29, to Peter asking what reward there will be for one who leaves earthly things for Christ, Christ answers : He shall receive a hundredfold, and shall possess life everlasting. And cap. XX, he explains it by the example of the father of a family who renders to his laborers a day's denarius as the reward of slight labor. Hebr., XIII, 16 : Do not forget beneficence and fellowship ; for by such hosts God is merited. II Tim., IV, 8 : There is laid up for me a crown of justice, which the Lord, the just judge, will render to me. Hebr., VI, 10 : For God is not unjust, that he should forget your work. And similarly elsewhere. Therefore, according to Scripture, there is promised to the good works of the just, not some kind of reward whatever, as the sectaries say, but eternal life itself ; not from mere liberality and mercy, as others say, but from justice, and therefore with merit properly so called.

Christ : You shall receive a hundredfold, and shall possess life everlasting. And chapter XX explains this by the example of the householder who gives the laborers a daily denarius as the reward of slight toil. Hebr., XIII, 16 : Do not forget beneficence and communication ; for by such sacrifices God is merited. II Tim., IV, 8 : As to the rest, there is laid up for me a crown of justice, which the Lord, the just judge, will render to me in that day. Hebr., VI, 10 : For God is not unjust, that he should forget your work. And so elsewhere passim. Therefore, according to Scripture, there is promised to the good works of the just, not a reward of whatever kind, as the sectaries say, but life eternal itself ; not from mere liberality and mercy, as others say, but from justice, and therefore as merit properly so called.

It is proved 2°. God confers on man through grace the virtue of acting well, and promises to his works done through grace a certain reward, indeed glory itself, as has been said ; all the other conditions required for merit can concur, for none is repugnant. Therefore man can merit even glory itself.