Summa Theologiae Moralis, vol. I: De Principiis

On the Matter of Human Law.

S. Th. I-II, q. 96, a. 1, 2, 3.

279. Principle. Law must be proportioned to the end which is the common good (n. 272), and therefore the matter about which civil law is concerned are all the acts whose positing or omission is useful for the common good, even those which are in themselves indifferent, inasmuch as they can be ordered to virtue and good, or to vice and evil. Now the common good consists of many things : 1) for society is constituted of many persons, 2) it is ordered to a good which consists in many affairs, to be procured through manifold actions, 3) it is instituted not that it may last for some moderate time, but that it may persevere for all time through the succession of citizens. Therefore law must procure the good not of some but of many, not in some one thing or action but in many, not for some time but in a manner of itself perpetual.

280. The acts useful for the common good are only :

1. Moral acts that are possible, i.e. not too difficult and burdensome, but accommodated to the powers of men (having regard to their frailty not only in general but also for their special condition and circumstances), otherwise the law would not be conformed to reason nor would it promote the public good, but would often be an occasion of sins, since it would be observed by few. Hence :

a) Heroic acts cannot be prescribed, except in an extraordinary public necessity (e.g. a law could prescribe to physicians in time of plague that they remain in the city), or unless someone has freely chosen a state to which it pertains.

b) Although any law can forbid any vices, it does not however forbid them all together or all vicious acts : for the law must be imposed on a multitude of men according to their condition, so that it is possible for them ; but in a multitude the greater part is imperfect, and therefore not all vices are forbidden, but only the graver ones, from which it is possible for the greater part of the multitude to abstain, and especially those which harm others, such as homicide, theft, etc., without whose prohibition society cannot be preserved.

2. Acts in some way external : for by these alone does man behave well or badly toward others constituting the city, for society arises from external relations ; whence only external and not merely internal acts are directly necessary or useful for the end, which is the peace by which citizens may tranquilly use their rights, and public prosperity.

Internal acts can however be prescribed indirectly and accidentally, inasmuch as they are joined with external ones and are manifested by them, e.g. if they are necessary so that the external acts be human, good, not feigned, etc. : for the law can prescribe only morally good acts.

3. Future acts, whence it is said : Law has no eyes backwards, and « The law provides only for the future ; it has no retroactive effect » (C. Civ., a. 2).

Thus a) according to directive force : since law is a rule of things to be done, by its nature it regards future acts, not past ones, which cannot be regulated ; for to prescribe, forbid, permit, or if irrevocable to invalidate past acts would be useless. Likewise b) also ordinarily according to coercive force : because namely it is very odious, past acts regularly cannot be punished, nor revocable ones invalidated, unless they were already forbidden by some law, or because of a great necessity of the common good : for in this case any good of a part can be exacted for the good of the whole, but it will be rather an imposition of a burden than a penalty. Hence the legislator cannot affect past acts, except a) in a penal law which imposes a penalty on an act already forbidden (at least by natural law) ; β) in a law establishing not a penalty but an incapacity, if the reason of the common good requires ; γ) in a law merely declaratory of a prior law.

281. The common good is manifold :

1. One thing civil society intends immediately, namely its own perfection and that of its members and temporal happiness, i.e. to institute, preserve, and perfect by promotion to better things, a good life in the multitude. To this pertain both the goods of society itself : constitution, government, administration, defense, and the relations of citizens to it and among themselves ; and the goods of the members : a) goods of the intellect : instruction in letters, sciences, human arts (which greatly contribute to private and public good) ; — b) goods of the will : to restrain delicts, oppose vices, promote virtues, and indeed all of them : for all that there are, just as they can be referred to private good, so also to the common good, just as all vices can be opposed to it, and therefore there is no virtue of whose acts the law cannot prescribe. It does not however prescribe about all the acts of all virtues, but only about those that are more orderly to the common good, either immediately as those that are done directly for the common good, or mediately as some are ordered by the legislator to good discipline, by which citizens are formed so that they preserve the common good of justice and peace. Hence human law does not prescribe except acts of justice, and acts of the other virtues inasmuch as they take on the character of justice ; — c) goods of the body : public health and due propagation ; — d) goods of fortune and those that contribute to the acquisition, transmission, abundance of things, industries, agriculture, and commerce.

2. Another thing society intends only mediately, namely eternal happiness, and therefore although it must procure temporal goods in such a way that they harm not the eternal, indeed that they procure them, it cannot however enact law immediately about spiritual things ; nor about mixed things unless it be in agreement with religious society.

282. Remark. — In all the aforesaid matters it can either instill natural and divine law, e.g. by compelling parents to nourish their minor children, and children to provide sustenance for their parents ; — or determine what it leaves indeterminate, e.g. by establishing conditions for succession in the goods of the deceased, or the manner of exercising justice ; — or impose what is conformed to it, e.g. prescription of goods, community or separation of goods in matrimony, rescission of a contract entered into by minors ; — or prescribe or forbid what it itself permits, e.g. with respect to fishing, the manufacture of liquors, or hunting ; — or urge all these things with an added penalty ; — or also impose conditions for the validity of acts established by it (e.g. with respect to contracts) ; in no way however can it contradict a superior law.