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.
Obj. 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.
Obj. 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.
Now a certain order is to be found in those things that are
apprehended universally. For that which, before aught else, falls
under apprehension, is _being_, the notion of which is included in
all things whatsoever a man apprehends. Wherefore the first
indemonstrable principle is that "the same thing cannot be affirmed
and denied at the same time," which is based on the notion of _being_
and _not-being:_ and on this principle all others are based, as is
stated in _Metaph._ iv, text. 9. Now as _being_ is the first thing
that falls under the apprehension simply, so _good_ is the first
thing that falls under the apprehension of the practical reason,
which is directed to action: since every agent acts for an end under
the aspect of good. Consequently the first principle of practical
reason is one founded on the notion of good, viz. that "good is that
which all things seek after." Hence this is the first precept of law,
that "good is to be done and pursued, and evil is to be avoided." All
other precepts of the natural law are based upon this: so that
whatever the practical reason naturally apprehends as man's good (or
evil) belongs to the precepts of the natural law as something to be
done or avoided.
Since, however, good has the nature of an end, and evil, the nature
of a contrary, hence it is that all those things to which man has a
natural inclination, are naturally apprehended by reason as being
good, and consequently as objects of pursuit, and their contraries as
evil, and objects of avoidance. Wherefore according to the order of
natural inclinations, is the order of the precepts of the natural
law. Because in man there is first of all an inclination to good in
accordance with the nature which he has in common with all
substances: inasmuch as every substance seeks the preservation of its
own being, according to its nature: and by reason of this
inclination, whatever is a means of preserving human life, and of
warding off its obstacles, belongs to the natural law. Secondly,
there is in man an inclination to things that pertain to him more
specially, according to that nature which he has in common with other
animals: and in virtue of this inclination, those things are said to
belong to the natural law, "which nature has taught to all animals"
[*Pandect. Just. I, tit. i], such as sexual intercourse, education of
offspring and so forth. Thirdly, there is in man an inclination to
good, according to the nature of his reason, which nature is proper
to him: thus man has a natural inclination to know the truth about
God, and to live in society: and in this respect, whatever pertains
to this inclination belongs to the natural law; for instance, to shun
ignorance, to avoid offending those among whom one has to live, and
other such things regarding the above inclination.
Reply Obj. 1: All these precepts of the law of nature have the
character of one natural law, inasmuch as they flow from one first
precept.
Reply Obj. 2: All the inclinations of any parts whatsoever of human
nature, e.g. of the concupiscible and irascible parts, in so far as
they are ruled by reason, belong to the natural law, and are reduced
to one first precept, as stated above: so that the precepts of the
natural law are many in themselves, but are based on one common
foundation.
Reply Obj. 3: Although reason is one in itself, yet it directs all
things regarding man; so that whatever can be ruled by reason, is
contained under the law of reason.
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