Summa Theologiae Moralis, vol. I: De Principiis

S. Th. I-II, q. 93, a. 3-6.

241. Thesis. From the eternal law all others are derived. — It is proved :

In ordered movers, the power of the second mover is derived from the power of the first mover, because the second does not move except inasmuch as it is moved by the first ; whence in a well-ordered state the reason of governance is derived from the first governor to the secondary ones, and in an art the reason of the things to be made is derived from the architect to the inferior artificers. But the eternal law is the reason of governance in the first and supreme governor.

Therefore all the reasons of governance, or laws, in the inferior governors are derived from the eternal law.

For : a) Human reason, in order that it be the rule of the will and of human acts, has [its force] from the divine reason or eternal law, of which it is a participation (q. 19, a. 4) ; therefore if a law ought to be conformed to reason, much more to the eternal law.

b) The first is indeed the measure of others. But the eternal law, or divine reason, precedes every other reason or law as a source. Therefore it is the first rule of every reason and law. And therefore honesty is to be esteemed chiefly from commensuration to that rule.

The eternal law, namely, is law by essence ; all others are law by participation, which are derived from it and indeed in a threefold way :

1° they are derived from the eternal law as from an exemplar cause, because all laws, in order that they be just, must be conformed to right reason and so to the eternal law, so that from the eternal law they have that they are a norm of rectitude ;

2° they are derived from the eternal law as from an efficient cause from which they have the force of obliging, because every inferior legislative power is from God, according to that of Rom. XIII, 1 : There is no power except from God : so from the eternal law they have that they are a norm of obligation.

Both of these the divine wisdom signified when it said (Prov. VIII, 15-16) : « By me kings reign (as to the second : power) and lawgivers decree what is just (as to the first : rectitude) ; by me princes rule and the mighty decree justice ». Hence all laws also

3° depend on and are derived from the eternal law as from a directive and actually regulative cause, because the eternal law, by means of the light of reason, directs legislators, so that they may see what laws according to diverse circumstances are to be instituted : so from the eternal law they have that they are actually instituted.

242. To the eternal law are subject all things that are subject to divine governance :

1. All natural things, whether necessary or contingent : for God has given not only to intellectual creatures a rule (which is a principle of acting), imprinting on their mind the knowledge of the divine precept, but to the whole nature principles and constituted [them] to their proper acts ; and therefore he is said to command the whole nature. Thus all the motions and actions of the whole nature are subject to the eternal law inasmuch as all creatures are inclined and moved by divine providence ; likewise the defects that occur in nature against the order of one or another particular cause, because these do not occur against the order of the first cause but are also subject to divine providence, from which nothing escapes.

2. All human things : for men are subject to the eternal law, not only as to the inclination to that which is conformed to the eternal law, but also because they have knowledge of the law : the wicked, imperfectly, in whom the natural inclination to virtue is corrupted by a vicious habit, and the natural knowledge of good is darkened by passions and vices ; the good, however, perfectly, because in them to the natural inclination to good is added the interior motive of grace and virtue, and to the natural knowledge of good is added the knowledge of faith and the gift of wisdom. Hence the good always act according to the law (in act or in habit), but the wicked often act against it ; yet insofar as they fall away from it on the part of action, so much the more are they subject to it on the part of passion, because so much the more must they be punished according to it¹.

3. But those things which pertain to the divine nature or essence are not subject : for these are really the eternal law itself. For the act of the mind does not really differ from God himself ; but nothing can be subject to itself.

Nor does it stand in the way that God is held not to do a moral evil, e.g. to lie : for he is not held to this by the force of any law prohibiting it, but by reason of the repugnance which arises from his nature and perfection, inasmuch as if he did evil or lied, he would not be God. Whence it is said that « God is to himself a law » (I, q. 21, a. 1, ad 2), not properly because nothing can be subject to itself, but because he is of himself right without law, as if he were to himself a law.