Section — Prümmer, Manuale Theologiae Moralis
3. On The Possessor In Doubtful Faith
Notion. A possessor in doubtful faith is one who, from a grave reason, positively doubts whether the thing which he possesses is his own or another's. Light doubts, therefore, since they are to be spurned, do not render the possessor one in doubtful faith. But a grave doubt concerning the ownership of a thing can either supervene afterward or be present from the beginning of the possession; or in other words: doubtful faith can be either supervening or antecedent.
221. 1. Obligations in the case of supervening doubtful faith.
The possessor, when a serious doubt has arisen, ought diligently to investigate the truth so that he may lay aside the doubt. For otherwise he exposes himself to the danger of retaining another's thing; indeed he also becomes a possessor in bad faith with the same obligations which were indicated in the preceding number. But after diligent inquiry has been made:
a) if it is morally established that the thing is another's, he ought to restore it as quickly as possible, according to what was said above concerning the possessor in good faith;
b) but if the doubt persists, he can retain the thing, because in doubt the condition of the possessor is better;69
c) if the owner afterward appears, he ought to restore the thing if it still exists; otherwise he ought to restore that in which he has been made richer, unless nevertheless in the meantime legitimate prescription has procured true ownership for him. Generally he then has all the rights and all the obligations of a possessor in good faith;
d) if the possessor has a probable opinion in his favor and a more probable opinion against himself, he can still retain the thing for himself. The reason is that no one ought to be thrust from his possession unless it is morally certain that he is not the legitimate possessor. But in the case this moral certitude is not present.
69 S. Alph., Theol. mor. l. 3, n. 511.
222. 2. Obligations in the case of antecedent doubtful faith.
a) He who, from a doubtful title, despoils a possessor in good faith of his thing sins against justice and is held to restore the thing seized to the former possessor.70 The reason is that in doubt the condition of the possessor is better.
b) But he who did not despoil the possessor against his will, but received the thing by a title legitimate of itself (purchase, donation, inheritance, etc.) from a possessor of doubtful or suspect faith, is held to make diligent inquiry. But if, after such inquiry has been made, he remains uncertain, he is more probably held to restore in proportion to the doubt, and indeed to the probable owner if he can be found; otherwise he ought to distribute the thing received to the poor or to pious causes. The reason is that he cannot retain the whole, since he began possession with doubtful faith; yet neither ought he to restore the whole, because it is not equitable to oblige him to so great a loss when it is truly doubtful whether the thing possessed is another's. Thus theologians commonly after St. Alphonsus.71
The contrary opinion, however, which exempts the possessor even in this case from the obligation of restitution, is defended by Cardinal d'Annibale, and indeed with arguments not to be spurned.72 Hence, e.g., if someone buys some thing concerning which he greatly doubts whether it can legitimately be sold by the seller, he indeed sins; but if afterward, inquiry having been made, the doubt remains, he ought indeed to be admonished, but not compelled, to restore the whole or a part.
c) He who received a thing or right (e.g., an inheritance) from a possessor in good faith and began to possess with doubt can, while the doubt remains, protect himself by the right of his predecessor; namely, he can possess in good faith and therefore is held to nothing until the contrary is certainly proved.
70 Cf. Billuart, De iure et iust. diss. 8, a. 9, § 5.
71 Theol. mor. l. 3, n. 625.
72 Summula Theol. mor. II, n. 121.