Saint Thomas Aquinas' Summa Theologica: Part I-II (Pars Prima Secundae), Question 94, Articles 4-6

Question 94 of the Natural Law

We must now consider the natural law; concerning which there are six points of inquiry:

1. What is the natural law?

2. What are the precepts of the natural law?

3. Whether all acts of virtue are prescribed by the natural law?

4. Whether the natural law is the same in all?

5. Whether it is changeable?

6. Whether it can be abolished from the heart of man?

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Fourth Article (I-II, Q. 94, Art. 4)

Whether the Natural Law Is the Same in All Men?

Objection 1: It would seem that the natural law is not the same in all. For it is stated in the Decretals that "the natural law is that which is contained in the Law and the Gospel". But this is not common to all men; because, as it is written, "all do not obey the gospel". Therefore the natural law is not the same in all men.

Objection 2: Further, "Things which are according to the law are said to be just," as stated in Ethic. v. But it is stated in the same book that nothing is so universally just as not to be subject to change in regard to some men. Therefore even the natural law is not the same in all men.

Objection 3: Further, as stated above, to the natural law belongs everything to which a man is inclined according to his nature. Now different men are naturally inclined to different things; some to the desire of pleasures, others to the desire of honors, and other men to other things. Therefore there is not one natural law for all.

On the contrary, Isidore says: "The natural law is common to all nations".

I answer that, As stated above, to the natural law belong those things to which a man is inclined naturally: and among these it is proper to man to be inclined to act according to reason. Now the process of reason is from the common to the proper, as stated in Phys. i. The speculative reason, however, is differently situated in this matter, from the practical reason. For, since the speculative reason is busied chiefly with necessary things, which cannot be otherwise than they are, its proper conclusions, like the universal principles, contain the truth without fail. The practical reason, on the other hand, is busied with contingent matters, about which human actions are concerned: and consequently, although there is necessity in the general principles, the more we descend to matters of detail, the more frequently we encounter defects. Accordingly then in speculative matters truth is the same in all men, both as to principles and as to conclusions: although the truth is not known to all as regards the conclusions, but only as regards the principles which are called common notions. But in matters of action, truth or practical rectitude is not the same for all, as to matters of detail, but only as to the general principles: and where there is the same rectitude in matters of detail, it is not equally known to all.

It is therefore evident that, as regards the general principles whether of speculative or of practical reason, truth or rectitude is the same for all, and is equally known by all. As to the proper conclusions of the speculative reason, the truth is the same for all, but is not equally known to all: thus it is true for all that the three angles of a triangle are together equal to two right angles, although it is not known to all. But as to the proper conclusions of the practical reason, neither is the truth or rectitude the same for all, nor, where it is the same, is it equally known by all. Thus it is right and true for all to act according to reason: and from this principle it follows as a proper conclusion, that goods entrusted to another should be restored to their owner. Now this is true for the majority of cases: but it may happen in a particular case that it would be injurious, and therefore unreasonable, to restore goods held in trust; for instance, if they are claimed for the purpose of fighting against one's country. And this principle will be found to fail the more, according as we descend further into detail, e.g. if one were to say that goods held in trust should be restored with such and such a guarantee, or in such and such a way; because the greater the number of conditions added, the greater the number of ways in which the principle may fail, so that it be not right to restore or not to restore.

Consequently we must say that the natural law, as to general principles, is the same for all, both as to rectitude and as to knowledge. But as to certain matters of detail, which are conclusions, as it were, of those general principles, it is the same for all in the majority of cases, both as to rectitude and as to knowledge; and yet in some few cases it may fail, both as to rectitude, by reason of certain obstacles (just as natures subject to generation and corruption fail in some few cases on account of some obstacle), and as to knowledge, since in some the reason is perverted by passion, or evil habit, or an evil disposition of nature; thus formerly, theft, although it is expressly contrary to the natural law, was not considered wrong among the Germans, as Julius Caesar relates.

Reply Objection 1: The meaning of the sentence quoted is not that whatever is contained in the Law and the Gospel belongs to the natural law, since they contain many things that are above nature; but that whatever belongs to the natural law is fully contained in them. Wherefore Gratian, after saying that "the natural law is what is contained in the Law and the Gospel," adds at once, by way of example, "by which everyone is commanded to do to others as he would be done by".

Reply Objection 2: The saying of the Philosopher is to be understood of things that are naturally just, not as general principles, but as conclusions drawn from them, having rectitude in the majority of cases, but failing in a few.

Reply Objection 3: As, in man, reason rules and commands the other powers, so all the natural inclinations belonging to the other powers must needs be directed according to reason. Wherefore it is universally right for all men, that all their inclinations should be directed according to reason.

Fifth Article (I-II, Q. 94, Art. 5)

Whether the Natural Law Can Be Changed?

Objection 1: It would seem that the natural law can be changed. Because on Ecclus. 17:9, "He gave them instructions, and the law of life," the gloss says: "He wished the law of the letter to be written, in order to correct the law of nature". But that which is corrected is changed. Therefore the natural law can be changed.

Objection 2: Further, the slaying of the innocent, adultery, and theft are against the natural law. But we find these things changed by God: as when God commanded Abraham to slay his innocent son; and when he ordered the Jews to borrow and purloin the vessels of the Egyptians; and when He commanded Osee to take to himself "a wife of fornications". Therefore the natural law can be changed.

Objection 3: Further, Isidore says that "the possession of all things in common, and universal freedom, are matters of natural law". But these things are seen to be changed by human laws. Therefore it seems that the natural law is subject to change.

On the contrary, It is said in the Decretals: "The natural law dates from the creation of the rational creature. It does not vary according to time, but remains unchangeable".

I answer that, A change in the natural law may be understood in two ways. First, by way of addition. In this sense nothing hinders the natural law from being changed: since many things for the benefit of human life have been added over and above the natural law, both by the Divine law and by human laws.

Secondly, a change in the natural law may be understood by way of subtraction, so that what previously was according to the natural law, ceases to be so. In this sense, the natural law is altogether unchangeable in its first principles: but in its secondary principles, which, as we have said (A. 4), are certain detailed proximate conclusions drawn from the first principles, the natural law is not changed so that what it prescribes be not right in most cases. But it may be changed in some particular cases of rare occurrence, through some special causes hindering the observance of such precepts, as stated above.

Reply Objection 1: The written law is said to be given for the correction of the natural law, either because it supplies what was wanting to the natural law; or because the natural law was perverted in the hearts of some men, as to certain matters, so that they esteemed those things good which are naturally evil; which perversion stood in need of correction.

Reply Objection 2: All men alike, both guilty and innocent, die the death of nature: which death of nature is inflicted by the power of God on account of original sin, according to 1 Samuel 2:6: "The Lord killeth and maketh alive". Consequently, by the command of God, death can be inflicted on any man, guilty or innocent, without any injustice whatever. In like manner adultery is intercourse with another's wife; who is allotted to him by the law emanating from God. Consequently intercourse with any woman, by the command of God, is neither adultery nor fornication. The same applies to theft, which is the taking of another's property. For whatever is taken by the command of God, to Whom all things belong, is not taken against the will of its owner, whereas it is in this that theft consists. Nor is it only in human things, that whatever is commanded by God is right; but also in natural things, whatever is done by God, is, in some way, natural, as stated in the First Part, Q. 105, A. 6, ad 1.

Reply Objection 3: A thing is said to belong to the natural law in two ways. First, because nature inclines thereto: e.g. that one should not do harm to another. Secondly, because nature did not bring in the contrary: thus we might say that for man to be naked is of the natural law, because nature did not give him clothes, but art invented them. In this sense, "the possession of all things in common and universal freedom" are said to be of the natural law, because, to wit, the distinction of possessions and slavery were not brought in by nature, but devised by human reason for the benefit of human life. Accordingly the law of nature was not changed in this respect, except by addition.

Sixth Article (I-II, Q. 94, Art. 6)

Whether the Law of Nature Can Be Abolished from the Heart of Man?

Objection 1: It would seem that the natural law can be abolished from the heart of man. Because on Rom. 2:14, "When the Gentiles who have not the law," etc. a gloss says that "the law of righteousness, which sin had blotted out, is graven on the heart of man when he is restored by grace". But the law of righteousness is the law of nature. Therefore the law of nature can be blotted out".

Objection 2: Further, the law of grace is more efficacious than the law of nature. But the law of grace is blotted out by sin. Much more therefore can the law of nature be blotted out.

Objection 3: Further, that which is established by law is made just. But many things are enacted by men, which are contrary to the law of nature. Therefore the law of nature can be abolished from the heart of man.

On the contrary, Augustine says: "Thy law is written in the hearts of men, which iniquity itself effaces not". But the law which is written in men's hearts is the natural law. Therefore the natural law cannot be blotted out.

I answer that, As stated above, there belong to the natural law, first, certain most general precepts, that are known to all; and secondly, certain secondary and more detailed precepts, which are, as it were, conclusions following closely from first principles. As to those general principles, the natural law, in the abstract, can nowise be blotted out from men's hearts. But it is blotted out in the case of a particular action, in so far as reason is hindered from applying the general principle to a particular point of practice, on account of concupiscence or some other passion, as stated above. But as to the other, i.e. the secondary precepts, the natural law can be blotted out from the human heart, either by evil persuasions, just as in speculative matters errors occur in respect of necessary conclusions; or by vicious customs and corrupt habits, as among some men, theft, and even unnatural vices, as the Apostle states, were not esteemed sinful.

Reply Objection 1: Sin blots out the law of nature in particular cases, not universally, except perchance in regard to the secondary precepts of the natural law, in the way stated above.

Reply Objection 2: Although grace is more efficacious than nature, yet nature is more essential to man, and therefore more enduring.

Reply Objection 3: This argument is true of the secondary precepts of the natural law, against which some legislators have framed certain enactments which are unjust.