Summa Theologiae Moralis, vol. I: De Principiis

On the Quality and Extension of the Obligation of Preceptive Law.

344. Preceptive or moral law is that which prescribes some good to be done or forbids some evil to be avoided. The observance of this law is not always an act of that species and virtue to which the matter of itself pertains, but of that from whose formal motive the law is enacted : for virtues and good human acts are distinguished by the formal object or motive. Thus fasting of itself is an act of abstinence, and the Lenten fast which is prescribed from such a motive, but the fast before communion is an act of religion which is imposed from the formal motive of religion. Whence he who transgresses the precept sins against that virtue from whose motive the precept is enacted.

From these it follows that the transgression of the precept is only a sin of formal disobedience if it is done from a special motive of obedience, but not in other cases, unless the transgression be from contempt. No ecclesiastical law seems to be enacted from a special motive of obedience.

345. Preceptive law founded on a presumption of law is that which rests on a reasonable conjecture or probability drawn from the circumstances often connected with the truth. For presumption is a probable conjecture of an uncertain thing (can. 1825 § 1) : thus e.g. a law obliging to abide by the judgment of a judge which is presumed to be just, to the execution of a contract which is supposed to have been validly entered into unless the contrary be proved ; likewise a law by which a boy is considered to have the use of reason from the age of seven (c. 88 § 3), an adolescent to know what matrimony is¹ (c. 1082 § 2).

Another is founded on a presumption of a particular fact when the superior presumes a fact, e.g. damage, fraud, consent, negligence not in general for the most part but in any particular case to exist, and therefore enacts a law for all similar cases : thus in the examples given ; — another is on a presumption of common danger when he presumes from such a work or manner of acting for the most part, ordinarily and commonly, damage, fraud, scandal, etc. to follow, and therefore forbids it, e.g. reading bad books : the fraud or scandal or damage is not supposed, but the danger of them.

The first of itself does not oblige, if the presumption in a particular case is false, because then the foundation of the law, which is the presumption of this particular fact, is lacking ; hence you are not bound to pay money for damage falsely presumed.

Whence the saying : the judgment is the same in the forum of conscience and in the external forum, is true in cases in which the external forum does not rest on a false presumption of a particular fact. Accidentally however in the external forum we are bound to obey, by reason of public order and of scandal, but then we can compensate ourselves secretly (even after the judgment of the judge) ; but we cannot obey if the thing be illicit, as if someone were to pay or render what is due in a marriage certainly invalid which is presumed valid in the external forum.

The second of itself always obliges, even in particular cases in which damage or its danger does not intervene, because the foundation of the law remains.

a) For the superior did not enact the law because he presumes damage in every case, but because he presumes it to be so commonly for men ; therefore as long as the common danger remains, so long does the law itself remain.

b) Otherwise the common good requires that no exception be admitted, otherwise evils to be avoided would not be efficaciously prevented because easily each one would persuade himself that in his regard there is no danger, which false persuasion the law intends to prevent, and likewise to render men diligent in avoiding damages. Thus ecclesiastical law enacted to prevent the general danger of perversity or spiritual detriment, just as civil law to prevent the general danger of negligence.

c) In other words : the law ceases only if the end ceases adequately, i.e. totally and with respect to all. But in the case, even if the danger does not exist for the individual, it persists for the community. Therefore the law does not cease. For its end is to avoid the common danger ; now the common danger cannot be efficaciously and certainly avoided if the law is not urged absolutely and for all, since easily each one would persuade himself that the danger is not present for himself, from which the end of the law would be frustrated.

Whence just as civil law, to prevent the general danger of negligence, obliges one guilty of merely juridical fault to repair the damage, e.g. to pay for damage caused by a dog without moral fault, by which law the judgment of danger is withdrawn from the subjects ; — so also ecclesiastical law obliges when it prohibits religious profession before the age of 16, invalidates clandestine marriage, prohibits mixed marriages or books placed on the Index, even if it is established that no fraud, or defect of liberty, or damage is present. Which doctrine is already confirmed by can. 21.

346. Law founded on a fiction of law is not to be confused with law founded on a presumption².

For presumption is a reasonable conjecture in an uncertain matter, but a fiction of law is a provision whereby the legislator from a just cause establishes the same for a feigned case as another law does in a true case, e.g. that canons absent from the choir because of infirmity are considered as present as to the daily distributions (can. 420), or that the marriage by which previous offspring is legitimated is considered valid from the time of its conception or birth (can. 1117), or that offspring born in a marriage which is afterwards proved null is considered legitimate (can. 1114), or that an invalid marriage, if healed in the root, is considered valid from the beginning (can. 1138).

Presumption therefore rests on verisimilitude, fiction on equity ; — presumption is assumed in a doubtful case according to verisimilitude, fiction in a certain case contrary to truth.

Such a law, if it be just, obliges in conscience.

Note however that 1) fiction has place only in cases expressed in law,

2. fiction ought not to operate more in the feigned case than truth in the true case,

3. it does not hold beyond what is expressed in the law : thus for the deceased and the heir the unity of person is held as to the inheritance, not as to other things,

4. finally it is to be strictly interpreted.

347. Permissive law is not the absence of law nor mere license or simple tolerance, but a true law which positively acknowledges in man an internal, or at least external or juridical, liberty or capacity for doing something. Such a law obliges others not to impede the aforesaid acts, and judges not to punish them. Likewise a concessive law of rights obliges others not to deprive them of those [rights] or to impede them from legitimate action. It is not however a merely prohibitive law for others, but grants a special right, concedes a faculty or capacity.