Article I: On the Directive Force or Obligation of Natural Law

St. Thomas, I-II, q. 94, a. 2 and 3; q. 100, a. 1.

250. Natural law is one, containing several precepts. - Natural law, although by reason of the matter about which it is concerned it contains several precepts, nevertheless in itself is one, both because it tends to one ultimate end and because all those precepts are founded upon one first universal principle: Good is to be done, evil is to be avoided.

It is proved: human reason, both speculative and practical, is essentially deductive. But just as being is the first thing which is known by the intellect, so good is the first thing which is known by practical reason. Whence, just as the first speculative principle is founded on the notion of being: It is impossible for the same thing to be and not to be, so the first practical principle is founded on the notion of good: Good is to be done, evil is to be avoided; and therefore reason commands or prohibits nothing except what it naturally apprehends as good or evil.

1. Others establish a diverse first principle, for example: Live conformably to human nature considered according to all its essential respects (thus various scholastic manuals); or: Exhibit by free actions also the image of God absolutely holy, impressed upon you through the mode of rational nature (Carl Aeger); or: Preserve the right order of rational nature as divinely sanctioned (Meyer). But these things are to be done because they are good. Furthermore, at least they are not the first principle, because they are not first in the intellect, nor are they had among the common people, who nevertheless know natural law. But the Augustinians, such as Berti (De Theologicis Disciplinis, l. XX, c. 4, prop. 3), establish this: Love God as end and the rest on account of Him; but that is first in the ontological order, not in the logical order.

251. Order and division of precepts. - Natural law in a general mode embraces all those things which so befit or are repugnant to rational nature that for the conservation of order they are necessarily commanded or prohibited by the Creator of nature Himself; whence to natural law pertain all precepts to which we are obligated from the nature of the thing and independently of any positive law. Among these there is given a manifold order:

A. By reason of matter, in two ways:

a) according to the threefold natural inclination of man to the good, whether of natural being, that is, of preserving existence, or of animal life, for example, of procreating offspring, or of rational life proper to him.

For good has the notion of end; whence man has as goods all those things to which he has natural inclination. But in man there is a threefold inclination: 1) to good according to the nature which he has in common with all substances, which all seek the conservation of their own being; 2) to good according to the nature which he has in common with animals, such as procreation and education of offspring; 3) to goods according to the nature of reason, which are proper to him, for example, that he worship God and live in society.

Hence precepts are distinguished according to the nature of substance (abstinence, fortitude), according to the nature of animal (chastity, prudence), and according to the nature of man (religion, justice);

b) according to the threefold natural relation or order of man: 1) to God as to his first principle and ultimate end; 2) to himself, for he consists of a twofold part, of which one, the higher, must rule the lower part; 3) to neighbor: made social, man is destined to conjugal, domestic, and political society. Hence precepts are distinguished toward God, toward oneself, and toward neighbor, according as man is regarded as a created, rational, or social being.

Order to God is the order of subjection; order to neighbor is the order of equality and proximity, by which his person in himself or in his things is prohibited from being violated, and he himself is to be loved after the likeness of ourselves; the order of man to himself is the conformity of himself and of his faculties (of which he is not master) to reason and to rational nature and its proper end, and of subordination to the human species and the common good.

1. Vermeersch well observes, Theologia Moralis I, n. 240: a) that man is subordinated not only to the end but also to the order on account of the ultimate end; whence one who acts against inclination or order already begins to act against the end; b) and that this order is not immediately imposed upon individuals and through individuals upon nature, but upon individuals through nature: whence generally it is to be observed, even if in a particular case it would not be inconvenient or harmful for some individual, because it always remains of itself inconvenient to nature.

B. Formally, on the part of the mode in which they are contained in the law, or by reason of knowledge and of the logical nexus among the principles of the law of nature:

1. some are general, most universal, most common, indeterminate, self-evident, known to all from the mere understanding of the terms, for example: Good is to be done, evil is to be avoided; What you do not wish to be done to you, do not do to another; One must live according to reason; The Creator is to be obeyed; To each his own is to be rendered; The Supreme Good is to be loved; Injury is to be done to no one; Live conformably to your nature as a rational, created, social being, etc.

2. others are more proper and determined, particular, as conclusions deduced from the first principles, and these are:

a) either immediately, proximately, and evidently deduced from the first principles, which are the precepts of the Decalogue;

b) or more remote, which are deduced not so evidently but mediately and by many consequences, for example, that usury is unjust, that lying is always illicit, that an injury inflicted is not to be avenged by private authority, that found things are to be restored.

C. By reason of force and efficacy, or of necessity to the end, and of the ontological and real nexus:

1. St. Thomas, IV Sent. d. 33, q. 1, a. 1, and ad 8; a. 2; and III Sent. d. 37, a. 3.

1. some are precepts primarily intended, which nature altogether demands, because they are altogether necessary to the end which nature directly and principally intends: thus marriage is altogether necessary for due procreation and education of offspring;

2. others are secondarily intended, derived from the first, to which nature inclines much, which either are necessary, not indeed that the primary end be obtained, but that it be obtained decently, fittingly, more easily, or are necessary to a secondary end which nature intends not directly but concomitantly and subordinately to another: thus the unity of marriage befits the education of offspring and is necessary for the peace of the family.

Briefly: some precepts concern necessary things without which the moral order is impossible; others concern things very useful, which are not strictly necessary, so that the order can subsist without them, although less perfectly.

Hence, relative to the altogether ultimate and primary end of natural law, which is God and the love of God above all things, there are distinguished:

a) first precepts, which prescribe things strictly necessary to the love of God, or prohibit those things which directly impede it and turn away from it; of which:

1. some immediately state a necessary order, or repugnance, to the ultimate end, God: these are the precepts of the first table;

2. others immediately state a necessary order, or repugnance, to love of ourselves or of neighbor, but mediately to the ultimate end, insofar as they are means necessary from the nature of the thing to it: love of ourselves, indeed, because it is a necessary predisposition to the love of God and neighbor, since we cannot tend except to our own good, nor love someone except by imitating love of ourselves, and because our life is a necessary condition for obtaining the end; love of neighbor, because society is a means altogether necessary to men from the nature of the thing for obtaining the end, whence here belong those things which are necessary to society and without which it cannot subsist: these are the precepts of the second table.

All these things are gravely prescribed or prohibited as altogether necessary to the ultimate end or altogether opposed to it;

b) second precepts derived from the first, which prescribe those things which are necessary so that the end be obtained decently, better, and more easily, and prohibit those things which retard from it or cannot be referred to it, such as 1) those things which include a certain small irreverence toward God, and only fall short of the due mode of worship; 2) those which detract somewhat from justice or charity; or 3) those which only lack necessity or utility. These are lightly prescribed or prohibited, because they are not strictly necessary to the ultimate end nor do they turn away from it.

From the foregoing it is clear that the precepts which are primary or secondary in knowledge are not the same as those which are primary or secondary by necessity and by intention of nature; for many things secondary in knowledge, which are deduced from the first principles by conclusion (even remote), are primarily intended by nature, such as the prohibition of homicide, adultery, theft; whence one must carefully inspect in what sense those terms are used among authors.

1. Secondary precepts by reason of the universal precept can be primary in their own order, in this genus, according as they regard determined matters, because they regard the principal end of that genus, and are distinguished from secondary precepts, which regard a secondary end or something accessory to the principal end. Those things which are secondary comparatively to one end can be primary with respect to another. Whence, in order to conclude that a precept obligates lightly, one must see that under no respect is it primary.

252. The object of natural law is acts of virtues.

Acts of virtues, according to their genus, insofar as they are virtuous, all belong to the law of nature: for this comprehends all things to which man is inclined according to nature. But each thing is inclined to an operation suitable to its form; and the form of man is the rational soul. Whence man is naturally inclined to operating according to reason, which is to act according to virtue. But if virtuous acts are considered according to themselves, insofar as they are such or such, according to species, not all belong to the law of nature, because many are matters of counsel, or concern those things to which nature does not incline, but which men have discovered by inquiry of reason as useful for living well.

253. Subject of natural law. - Because natural law is implanted with rational nature and essentially joined to it, hence all rational creatures are subject to it and bound by it, not only adults (among whom are the blessed and the damned), but also children and the perpetually insane: these, however, are not bound perfectly and in second act, because they do not have the use of reason and knowledge of the law, but imperfectly and in first act, because they have potency to those things. Hence:

1. although in these there is no formal sin because the use of reason and liberty is lacking, nevertheless they sin materially, by acting against the law of nature habitually inhering in them;

2. the same must be said of those sleeping, drunk, and others who here and now are ignorant of the law, unless they have culpably placed the cause of sin; in which case they also sin formally;

3. those who induce the aforesaid to acting against natural law sin formally: for they are the moral or even physical cause of these sins, and therefore by their will they participate in and embrace them; for the action of the instrument is deservedly imputed to the principal agent. Add that they are often the cause of a bad custom in them, and of scandal in bystanders.