Section — Prümmer, Manuale Theologiae Moralis
§ 3. On a Law Founded upon False Presumption
216. Notion. Presumption is taken in diverse senses, as will be explained more broadly below in the treatise on hope. But presumption, as there is now question of it, can be defined: "a probable conjecture concerning an uncertain thing";130 or more broadly: "Presumption is a certain kind of proof, namely a reasonable conjecture or proof of a doubtful thing gathered from arguments and indications which frequently occur through the circumstances of things."131 Concerning presumptions, insofar as they constitute a certain kind of proof in ecclesiastical trials, canonists treat broadly, and there exists a special chapter in the Code of Canon Law.132 We briefly note the following:
130 Cod. iur. can. c. 1825, § 1.
131 Ferraris, Prompta Bibl., word "Praesumptio"; Cod. iur. can. c. 1825, § 1. In the German language presumption is called "Rechtsvermutung"; in the French language "présomption"; cf. French Civil Code 1349 sqq.
132 Book 4, title 10, chapter 6.
217. Divisions. 1. By reason of the authority by which it is made, presumption of man and presumption of law are distinguished. A presumption of man is that which is found in no written law, but is gathered by man from reasonable indications. Thus, for example, a judge condemns the accused because of indications so strong that they produce moral certitude of guilt, although strict proof is not present. Canonists divide this presumption of man into light, grave, and most grave, according as the indications are light, grave, or most grave. - A presumption of law is that which proceeds from the authority and precept of the law itself. Several presumptions are held in law, for example, everyone is presumed good unless he is proved evil; "once evil, he is always presumed to be evil"133 (understand: in the same kind of evil).
Presumption of law is subdivided into presumption iuris simply and presumption iuris et de iure. The first is that upon which the law indeed rests, but which admits proof of the contrary both direct and indirect; for example, true matrimonial consent is presumed conformable to the external words which were uttered in the celebration of marriage. Infants of Catholic parents are presumed to have been legitimately baptized. The other is that which in law is held as full truth until the contrary is manifestly established; and therefore against such a presumption only indirect proof is admitted, that is, proof against the fact which is the foundation of the presumption.134 Such a presumption iuris et de iure stands, for example, for the sentence of a judge which passes into a thing adjudged;135 for the validity of a marriage which has not been accused while both spouses were living.136
2. By reason of the object, presumption of common danger and of particular fact are distinguished. The first is present when the legislator presumes that in certain circumstances there is common danger or fault; for example, the legislator presumes that from the reading of heretical books there arises a common danger of perversion, and therefore he prohibits the reading of books of this kind. - The other presumption has place when the legislator presumes some particular fact, although this cannot be certainly proved; for example, in relation to marriage a doubtful baptism is presumed valid, although this cannot be proved in a particular case.
133 Rule of Law 8 in VI.
134 Cod. iur. can. c. 1826.
135 Ibid. c. 1904; res iudicata in German: rechtskräftiges Urteil; in French: jugement définitif et exécutoire.
136 Ibid. c. 1972.
218. Principle 1. A law founded upon the presumption of common danger obliges, even if the presumed danger is not really present in a particular case. Thus also the Code of Canon Law c. 21 expressly establishes.
The reason is that a law does not yet cease, even if its end ceases in some particular case, as will be explained more broadly below. And in truth an opening would be given to many and pernicious illusions if a law ceased whenever some subject thinks that the law is useless for him. Hence, for example, the ecclesiastical law prohibiting evil books obliges even him for whom in some particular case there is no danger of perversion; the law of matrimonial banns must be observed, even if in some particular case it is already morally established from the beginning that no impediment obstructs the marriage.
219. Principle 2. A law founded upon presumption of fact obliges in the external forum until the falsity of the fact has been proved; but in the internal forum a law of this kind does not oblige.
The reason for the first part is that the presumption did not arise from a light motive and therefore is rightly held as truth in the external forum for as long as its falsity has not been proved. - The reason for the second part is the common adage: "Presumption must yield to truth." Hence a hard conflict between the external and the internal forum can arise; for example, if some woman has been joined in marriage in the face of the Church, she is presumed in the external forum to be a true wife and is compelled to cohabit with the man until the nullity of the marriage has been manifestly proved; but if that woman herself certainly knows that the putative marriage is invalid because of some diriment impediment, she cannot conduct herself as a true wife and therefore cannot licitly ask or render the conjugal debt. But how she must act in such a case will be said below in the treatise on marriage III, n. 732 and 751.
220. Scholion. On legal fiction. From a law founded upon presumption differs the so-called "fiction of law," which is a disposition of law made in a possible matter against truth from a just cause.137 Therefore by a fiction of law the law declares from a just reason that some juridical effect has been produced by a cause which, because of an impediment, did not in reality produce it; or more briefly: fiction of law is an objective falsity and a mere juridical favor granted from a just cause. For example, since every marriage celebrated in the face of the Church is presumed valid, all infants begotten in such a marriage are deemed legitimate by a fiction of law, even if afterward the nullity of the marriage becomes known. Likewise, by a fiction of law, the so-called sanation "in the root" effects that a marriage hitherto invalid is held valid from the beginning. Such fictions of law already came into use in the old Roman law and, because they are conformable to natural equity, always oblige in both the external and the internal forum; but they must receive a strict interpretation and therefore must not be extended beyond that which is expressed in the law.
137 Cf. Bouquillon, Theol. mor. fund. n. 175 (ed. 3); fictio iuris is rechtliche Annahme in German.