All grace _ex vi termini_ is a free gift.(406) This applies particularly to Christian grace, which is so absolutely gratuitous that its gratuity, together with its necessity, may be called the groundwork of the Catholic religion.
1. STATE OF THE QUESTION.—To show what is meant by “gratuity” (_gratuitas_) we must first explain the technical term “merit.”
a) “Merit” (_meritum_=that which is earned) is that property of a good work which entitles the performer to receive a reward from him to whose advantage the work redounds.
α) An analysis of this definition shows that (1) merit is found only in such works as are positively good; (2) merit and reward are correlative terms which postulate each other; (3) merit supposes two distinct persons, one who deserves and another who awards; (4) the relation between merit and reward is based on justice, not on benevolence or mercy. The last-mentioned determination is by far the most important of the four.(407)
β) Ethics and theology clearly distinguish two kinds of merit: (1) condign merit,(408) which is merit in the strict sense (_meritum adaequatum sive de condigno_), and (2) congruous merit (_meritum inadaequatum sive de congruo_), so called because of the congruity, or fitness, that the claim should be recognized. Condign merit presupposes some proportion between the work done and the reward given in compensation for it (_aequalitas s. condignitas dati et accepti_). It is measured by commutative justice and thus confers a real claim to a reward. For example, a conscientious workman has a strict claim to his wage. Owing to the lack of intrinsic proportion between service and reward, congruous merit can claim a remuneration only on grounds of fairness.
A distinction between these two kinds of merit was already made by the Fathers, though not in the terms of present-day theology. It was known to the older Scholastics and emphasized anew by Luther’s famous adversary Johann Eck.(409)
No relation of strict justice is conceivable between the Creator and His creatures. On the part of God there can only be question of a gratuitous promise to reward certain good works,—which promise He is bound to keep because He is veracious and faithful.(410)