OF THE NATURAL LAW (SIX ARTICLES)
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?
Whether the natural law is a habit?
Objection 1: It would seem that the natural law is a habit. Because, as the Philosopher says (Ethic. ii, 5), "there are three things in the soul: power, habit, and passion." But the natural law is not one of the soul's powers: nor is it one of the passions; as we may see by going through them one by one. Therefore the natural law is a habit.
Objection 2: Further, Basil [*Damascene, De Fide Orth. iv, 22] says that the conscience or "synderesis is the law of our mind"; which can only apply to the natural law. But the "synderesis" is a habit, as was shown in the FP, Q[79], A[12]. Therefore the natural law is a habit.
Objection 3: Further, the natural law abides in man always, as will be shown further on (A[6]). But man's reason, which the law regards, does not always think about the natural law. Therefore the natural law is not an act, but a habit.
On the contrary, Augustine says (De Bono Conjug. xxi) that "a habit is that whereby something is done when necessary." But such is not the natural law: since it is in infants and in the damned who cannot act by it. Therefore the natural law is not a habit.
I answer that, A thing may be called a habit in two ways. First, properly and essentially: and thus the natural law is not a habit. For it has been stated above (Q[90], A[1], ad 2) that the natural law is something appointed by reason, just as a proposition is a work of reason. Now that which a man does is not the same as that whereby he does it: for he makes a becoming speech by the habit of grammar. Since then a habit is that by which we act, a law cannot be a habit properly and essentially.
Secondly, the term habit may be applied to that which we hold by a habit: thus faith may mean that which we hold by faith. And accordingly, since the precepts of the natural law are sometimes considered by reason actually, while sometimes they are in the reason only habitually, in this way the natural law may be called a habit. Thus, in speculative matters, the indemonstrable principles are not the habit itself whereby we hold those principles, but are the principles the habit of which we possess.
Reply to Objection 1: The Philosopher proposes there to discover the genus of virtue; and since it is evident that virtue is a principle of action, he mentions only those things which are principles of human acts, viz. powers, habits and passions. But there are other things in the soul besides these three: there are acts; thus "to will" is in the one that wills; again, things known are in the knower; moreover its own natural properties are in the soul, such as immortality and the like.
Reply to Objection 2: "Synderesis" is said to be the law of our mind, because it is a habit containing the precepts of the natural law, which are the first principles of human actions.
Reply to Objection 3: This argument proves that the natural law is held habitually; and this is granted.
To the argument advanced in the contrary sense we reply that sometimes a man is unable to make use of that which is in him habitually, on account of some impediment: thus, on account of sleep, a man is unable to use the habit of science. In like manner, through the deficiency of his age, a child cannot use the habit of understanding of principles, or the natural law, which is in him habitually.
Whether the natural law contains several precepts, or only one?
Objection 1: It would seem that the natural law contains, not several precepts, but one only. For law is a kind of precept, as stated above (Q[92], A[2]). If therefore there were many precepts of the natural law, it would follow that there are also many natural laws.
Objection 2: Further, the natural law is consequent to human nature. But human nature, as a whole, is one; though, as to its parts, it is manifold. Therefore, either there is but one precept of the law of nature, on account of the unity of nature as a whole; or there are many, by reason of the number of parts of human nature. The result would be that even things relating to the inclination of the concupiscible faculty belong to the natural law.
Objection 3: Further, law is something pertaining to reason, as stated above (Q[90], A[1]). Now reason is but one in man. Therefore there is only one precept of the natural law.
On the contrary, The precepts of the natural law in man stand in relation to practical matters, as the first principles to matters of demonstration. But there are several first indemonstrable principles. Therefore there are also several precepts of the natural law.
I answer that, As stated above (Q[91], A[3]), the precepts of the natural law are to the practical reason, what the first principles of demonstrations are to the speculative reason; because both are self-evident principles. Now a thing is said to be self-evident in two ways: first, in itself; secondly, in relation to us. Any proposition is said to be self-evident in itself, if its predicate is contained in the notion of the subject: although, to one who knows not the definition of the subject, it happens that such a proposition is not self-evident. For instance, this proposition, "Man is a rational being," is, in its very nature, self-evident, since who says "man," says "a rational being": and yet to one who knows not what a man is, this proposition is not self-evident. Hence it is that, as Boethius says (De Hebdom.), certain axioms or propositions are universally self-evident to all; and such are those propositions whose terms are known to all, as, "Every whole is greater than its part," and, "Things equal to one and the same are equal to one another." But some propositions are self-evident only to the wise, who understand the meaning of the terms of such propositions: thus to one who understands that an angel is not a body, it is self-evident that an angel is not circumscriptively in a place: but this is not evident to the unlearned, for they cannot grasp it.