Third Question: On the Mutability of Natural Law

St. Thomas, I-II, q. 94, a. 4, 5, 6; q. 100, a. 1 and 8.

257. Natural law is one among all, regarded in first act: for the same habitual inclination of reason to judging rightly conformably to eternal law is present, whence there is the same participation and conformity with eternal law; but in second act, that is, as to actual judgments of reason:

1. it is altogether the same as to substance, that is, as to the most common principles;

2. but as to application, that is, as to proper principles deduced from the first principles, especially the more remote, it is the same among all generally and as in the greater number; yet because not all always judge and apply principles in the same way, therefore sometimes it is not the same as in the fewer cases, either:

a) as to subjective knowledge: for just as some are ignorant of deductions from speculative principles, so those having depraved reason are ignorant of these practical principles from passion, bad custom, or a bad disposition of nature;

b) also as to objective rectitude: deductions of speculative principles are necessary and the same among all, although they are not equally known by all; but practical reason is concerned with contingent things, in which human operations consist; whence, on account of particular impediments, sometimes principles cannot be rightly applied. Thus, for example, the principle "deposits are to be returned" would not be rightly applied if the depositor asked for return to the harm of himself or of another. And similar exceptions are given for preserving a secret or private dominion. Whence what is right in one case is not right in another.

258. Natural law is intrinsically immutable. - Although it can be changed by the addition of other laws, formally (according to the principles themselves or the tenor of the law) it is intrinsically immutable as to subtraction, so that nothing ceases to be of natural law which previously was of it: for it is founded in rational nature regarded with its necessary relations to other things, especially to the ultimate end, and arises necessarily from the nature of things; whence it contains only that which by its nature is intrinsically good or evil, necessarily leading to the ultimate end or turning away from it, independently of every positive will, even of God. Whence, just as its foundation in itself, its object, and its ultimate end are immutable, so also the law itself is immutable.

Nevertheless the matter of certain precepts, or its circumstances, can be changed; and when these are changed, the law no longer obtains. For some precepts are founded immediately and independently of every condition in the immutable essences themselves of things, and in these there is no change: for these regard those things which are essentially good or evil. But others are founded in the natural and ordinary conditions of things and regard those things which ordinarily and regularly are good or evil, yet not under every condition and for every case. For God through miracle can change the conditions of things which are the matter of the law, and secondary causes also can change the circumstances of things; when these are changed, the principles of the law and the law itself are not changed, but they are not applicable. Whence it can happen that the same action physically regarded which was commanded or prohibited by the law of nature here and now no longer is, because morally it is another, whether on account of a change of matter by a miracle of God, or on account of a change of circumstances.

Therefore 1) no change is given in natural law: a) as to the primary principles in knowledge, altogether general and immediately evident;

b) per se as to the principles primarily intended, which directly and immediately state a necessary order or repugnance to God, because they concern things essentially good and evil: for subjection to the first cause is immutable and order to the ultimate end altogether necessary. Those things are excepted which have had their origin from the free will of men, such as a vow and a promissory oath, whose obligation or debt, as not necessary of itself but voluntarily assumed, can be remitted by God, just as man can yield his voluntarily acquired right.

2. Change is not given generally and as in the greater number; but per se it can sometimes be given as in the fewer cases, in precepts which directly and immediately are concerned with means to the end, because ordinarily they depend upon some conditions. Thus:

a) as to principles primarily intended, for one or another particular case, if the conditions of things are changed (as in the case of a deposit or secret), or also if they can be changed miraculously by God: thus homicide, adultery, theft are evil, but the same actions could be licit if God removed from another the right to life, to the body of the spouse, or to temporal goods. Exception is made if exceptionally they are founded immediately in the essences of things, independently of every condition: thus sins of lust against nature and lying are always evil;

b) a fortiori as to principles secondarily intended, even commonly and for all, during some time: for although regularly they must be observed, nevertheless they can sometimes not obligate because of special causes, even natural ones, impeding their observance. Thus unity generally and per se befits the primary end and is necessary for the secondary end of marriage; nevertheless per accidens polygamy can be licit on account of propagation of the people. Marriage between brother and sister per se is evil, but it was licit at the beginning of the human race: for always an end of lesser moment must yield to the more principal, and a lesser precept to a greater.

Let it be noted further that most principles which are proposed in a general formula are expressed inadequately and are not universal, but include a restriction, condition, or determination understood beneath. Thus, for example, the precept, You shall not kill, adequately expressed, sounds: You shall not kill an innocent person by private authority and by way of aggression. Whence the exceptions of such a principle are only corrections of our mode of speaking, not of the law itself.

259. Natural law is extrinsically immutable or indispensable. - For God cannot change and abrogate it, because He cannot fail to command good or prohibit evil, and moreover His will would not suffice for changing law which is nature itself; but dispensation is a true change and as it were abrogation of the law, namely, its relaxation and the cessation of obligation in a particular case, made by one having power, while the matter of the law remains immutable. But if God is said to dispense, this must be understood improperly or indirectly, either a) of a change of matter, as when He yields His right and thus remits the obligation in a vow or oath, whereby it happens that the promised matter is withdrawn from the law saying that to each his own must be rendered; or b) of an authentic declaration and interpretation that the law does not obligate because of a change of circumstances, as was done for the polygamy of the patriarchs: for often it is dangerous to leave to men the judgment whether the circumstances are verified in which the law does not obligate, and then the power of declaring to what cases it ought not extend is reserved to the author of the law.

A fortiori the Church cannot change natural law or dispense in it. Nevertheless it can interpret it simply, that is, merely explain it, and indeed authentically and infallibly, both because natural law was also revealed and because it is the necessary foundation for Christian morals. It can also, in the name of God, dispense in a vow, oath, and marriage, but improperly, insofar as it declares that in certain cases the law no longer obtains, namely, that God yields His right or annuls the bond.

260. Natural law cannot be abolished from the heart of men, if it is considered in first act as the habitual light of reason; but in second act as to actual knowledge:

1. As to the primary principles in knowledge or the most universal principles, it cannot be abolished and be unknown, because they are self-evident and therefore altogether indelible; nevertheless in application we can err from passion.

2. As to the proper and particular principles proximately deduced from the first principles:

a) per se there is not ignorance in one who uses reason suitably developed, because they can be known with the easiest diligence (Rom. II, 16);

b) nevertheless per accidens there can be vincible ignorance, and even invincible ignorance for a short time, on account of impediments of reason, such as bad persuasions from insufficient development or cultivation of reason in children and the very uneducated, depraved customs, corrupted habits, etc., or also when there is question of the application of principles, especially if certain circumstances seem to make an evil act honorable;

c) indeed perhaps for a long time in the absence of any cultivation whatsoever.

3. As to more remote principles, because they are deduced only by subtler consideration and often require attention to multiple and complicated circumstances, there can be invincible ignorance even among the pious and learned, as experience shows.

Authors admit that the malice of internal acts can be invincibly unknown, namely, at least of depraved delights and perhaps also of desires, of an officious lie, of perjury for protecting life, of theft for relieving the needy, of pollution in boys, and of fornication.

261. Corollary.

Nothing excuses from a negative natural precept, not even danger of death, because it prohibits that which is intrinsically evil. From an affirmative natural precept a proportionately grave inconvenience excuses: for an affirmative law does not obligate at individual moments; therefore ordinarily it does not obligate precisely when grave inconvenience is present, but the moment can be awaited when it is not present. Nevertheless danger of death does not excuse from it in a case in which violation would yield either to great common damage (the common good is to be preferred to a private good), or to the extreme spiritual necessity of one's neighbor (the spiritual good of one's neighbor is to be preferred to one's own temporal good), or to hatred of God and religion or contempt of the Church; as will be said in its places.