Merit (Latin meritum), in general, is understood to be that property of a good work which entitles the doer to receive a reward (prœmium, merces) from him in whose service the work is done. By antonomastic usage, the word has come to designate also the good work itself, insofar as it deserves a reward from the person in whose service it was performed.
Condign merit supposes an equality between service and return; it is measured by commutative justice (justitia commutativa), and thus gives a real claim to a reward. Congruous merit, owing to its inadequacy and the lack of intrinsic proportion between the service and the recompense, claims a reward only on the ground of equity. This early-scholastic distinction and terminology, which developed in the controversies with the Pelagians and Semipelagians, were again emphasized by Johann Eck, the famous adversary of Martin Luther (cf. Greying, "Joh. Eck als junger Gelehrter," Münster, 1906, pp. 153 sqq.). The essential difference between meritum de condigno and meritum de congruo is based on the fact that, besides those works which claim a remuneration under pain of violating strict justice (as in contracts between employer and employee, in buying and selling, etc.), there are also other meritorious works which at most are entitled to reward or honour for reasons of equity (ex œquitate) or mere distributive justice (ex iustitia distributiva), as in the case of gratuities and military decorations. From an ethical point of view the difference practically amounts to this that, if the reward due to condign merit be withheld, there is a violation of right and justice and the consequent obligation in conscience to make restitution, while, in the case of congruous merit, to withhold the reward involves no violation of right and no obligation to restore, it being merely an offence against what is fitting or a matter of personal discrimination (acceptio personarum). Hence the reward of congruous merit always depends in great measure on the kindness and liberality of the giver, though not purely and simply on his good will.
In Christian theology, man possesses nothing of his own; all that he has and all that he does is a gift of God, and, since God is infinitely self-sufficient, there is no advantage or benefit which man can by his services confer upon Him. Hence on the part of God there can only be question of a gratuitous promise of reward for certain good works. For such works He owes the promised reward, not in justice or equity, but solely because He has freely bound himself, i.e., because of His own attributes of veracity and fidelity. It is on this ground alone that we can speak of Divine justice at all, and apply the principle: Do ut des (cf. St. Augustine, Serm. clviii, c. ii, in P. L., XXXVIII, 863).
Apart from earlier dogmatic declarations given in the Second Synod of Orange of 529 and in the Fourth Lateran Council of 1215 (see Denzinger, 191, 430), the Council of Trent upheld the traditional doctrine of merit by insisting that life everlasting is both a grace and a reward (Sess. VI, cap. xvi, in Denzinger, n. 809). It condemned as heretical Luther's doctrine of the sinfulness of good works (Sess. VI, can. xxv), and declared as a dogma that the just, in return for their good works done in God through the merits of Jesus, should expect an eternal reward (loc. cit., can. xxvi).
In order to be meritorious a work must be morally good, morally free, done with the assistance of actual grace, and inspired by a supernatural motive.
As to the second requisite, i. e., moral liberty, it is clear from ethics that actions, due to external force or internal compulsion, can deserve neither reward nor punishment. It is an axiom of criminal jurisprudence that no one shall be punished for a misdeed done without free will; similarly, a good work can only then be meritorious and deserving of reward when it proceeds from a free determination of the will. This is the teaching of Christ (Matt., xix, 21): "If thou wilt be perfect, go sell what thou hast, and give it to the poor, and thou shalt have treasure in heaven."
The necessity of the third condition, i. e., of the influence of actual grace, is clear from the fact that every act meriting heaven must evidently be supernatural just as heaven itself is supernatural, and that consequently it cannot be performed without the help of prevenient and assisting grace, which is necessary even for the just. The strictly supernatural destiny of the Beatific Vision, for which the Christian must strive, necessitates ways and means which lie altogether beyond what is purely natural (see GRACE).
Finally, a supernatural motive is required because good works must be supernatural, not only as regards their object and circumstances, but also as regards the end for which they are performed (ex fine). But, in assigning the necessary qualities of this motive, theologians differ widely. While some require the motive of faith (motivum fidei) in order to have merit, others demand in addition the motive of charity (motivum caritatis), and thus, by rendering the conditions more difficult, considerably restrict the extent of meritorious works (as distinguished from merely good works). Others again set down as the only condition of merit that the good work of the just man, who already has habitual faith and charity, be in conformity with the Divine law, and require no other special motive.
The agent who merits must fulfil two conditions: He must be in the state of pilgrimage (status viœ) and in the state of grace (status gratiœ). By the state of pilgrimage is to be understood our earthly life; death as a natural (although not an essentially necessary) limit, closes the time of meriting. The time of sowing is confined to this life; the reaping is reserved for the next, when no man will be able to sow either wheat or cockle. The opinion proposed by a few theologians (Hirscher, Schell), that for certain classes of men there may still be a possibility of conversion after death, is contrary to the revealed truth that the particular judgment (judicium particulare) determines instantly and definitively whether the future is to be one of eternal happiness or of eternal misery (cf. Kleutgen, "Theologie der Vorzeit", II, 2nd ed., Münster, 1872, pp. 427 sqq.). Baptized children, who die before attaining the age of reason, are admitted to heaven without merits on the sole title of inheritance (titulus hœreditatis); in the case of adults, however, there is the additional title of reward (titulus mercedis), and for that reason they will enjoy a greater measure of eternal happiness.
In addition to the state of pilgrimage, the state of grace (i. e., the possession of sanctifying grace) is required for meriting, because only the just can be "sons of God" and "heirs of heaven" (cf. Rom., viii, 17). In the parable of the vine Christ expressly declares the "abiding in him" a necessary condition for "bearing fruit": "He that abideth in me, and I in him, the same beareth much fruit" (John, xv, 5); and this constant union with Christ is effected only by sanctifying grace. In opposition to Vasquez, most theologians are of opinion that one who is holier will gain greater merit for a given work than one who is less holy, although the latter perform the same work under exactly the same circumstances and in the same way. The reason is that a higher degree of grace enhances the godlike dignity of the agent, and this dignity increases the value of the merit.
Merit requires on the part of God that He accept (in actu secundo) the good work as meritorious, even though the work in itself (in actu primo) and previous to its acceptance by God, be already truly meritorious. Theologians, however, are not agreed as to the necessity of this condition. The Scotists hold that the entire condignity of the good work rests exclusively on the gratuitous promise of God and His free acceptance, without which even the most heroic act is devoid of merit, and with which even mere naturally good works may become meritorious.