(i.e., the last seven of the Ten Commandments), is a consequence of original sin.5
But this theory had to be completely abandoned. For this type of argument was unable to furnish what it was intended to provide, namely, an ethico-philosophical explanation of the actions apparently contrary to the natural moral law recorded in the Old Testament. And so Alexander of Hales had recourse, as did St. Albert the Great and other contemporaries, to the doctrine of the primacy of the will in God as well as to God’s sovereign dominion that transcends all laws. These thinkers perceived clearly enough that in this way everything again became uncertain, but they were unable to prevent this outcome. For an adequate solution of the problem the genius of a Thomas Aquinas was needed.
St. Thomas (1225–74) starts from the likeness of human nature to the divine nature. Understanding and free will are the most essential marks that distinguish man from every other earthly creature. It is precisely through them that man is in a special degree the image and likeness of God. Man’s intellect and free will constitute the closest image of God in the material universe, His creation. St. Thomas, indeed, is fond of setting out from the notion of analogy of being: namely, that all created being, though of an altogether different kind from the divine Being, is an image of the latter and a participation in it—from merely inanimate being of inorganic nature up to man, whom God created after His own image.
Here teleology, the doctrine of ends or final causes, enters the scene.6 The essences of things, which are exemplifications of the ideas conceived by the divine intellect, constitute at the same time the end or goal of the things themselves. The perfection or fulfillment of the things is their essence: formal cause and end are one (causa finalis is ultimately identical with causa formalis). Accordingly in the essential nature of the created world, as it came forth in conformity with the will of the Creator, are imbedded also the norms of its being. In the essential nature is likewise founded essential oughtness, the eternal law, which is God’s wisdom so far as it directs and governs the world as first cause of all acts of rational creatures and of all movements of irrational beings. The eternal law, then, is the governance of the world through God’s will in accordance with His wisdom. This law is thus the order of this world. Creatures fulfill this law in conformity with their nature as it has been fashioned by God: from the lifeless and inorganic realm of creation, through the living but dumb creatures, to the rational and free beings.
The eternal law, therefore, comprises several elements. First, it includes what today we call the laws of the natural sciences: the laws of movement taken generally, in accordance with which the stars in the heavens and the stones upon earth are moved from without. Secondly, it embraces what in living creatures, plants and animals, we term the laws of their evolution and growth, the laws of reaction to external influences or stimuli, instinct, and the like, which, however, involve movement from within, after the manner of an entelechy.7 Thirdly, it contains the laws by virtue of which man, as a rational and free being, knows and wills, hence the laws of theoretical and practical reason. Since man is quodammodo omnia—herein consists his likeness to God, who is eminenter omnia—he is wholly subject to the eternal law in his material, sentient, and rational being, but ever in keeping with his essence. Oughtness, not blind compulsion and necessity, characterizes the way man obeys the law. Hence for man, as a free rational being, the eternal law becomes the natural moral law. Man must (i.e., ought to) thus both will and achieve the perfecting or fulfillment of the potentialities of his being which God has put into his nature, as he perceives them in virtue of his reason and becomes conscious of them.
Furthermore, this natural moral law is alone law in the proper sense: a norm which ought to be obeyed, not one that must be blindly obeyed. Our modern laws of nature are law only in a metaphorical sense. Law, indeed, is a norm and measure for acts which rational creatures alone are capable of. Its basic norm may be simply stated: Act in conformity with your rational nature. For rational nature, known through self-consciousness or reflex thinking, constitutes the ontological criterion of man’s oughtness. Through its free realization he becomes a man, a free rational being. God’s wisdom and knowledge as well as His will stand revealed in the essential idea of man.
St. Thomas reaches the same conclusion from still another consideration, from the metaphysical notion of goodness.8 Reason is the first and proximate rule for judging the moral quality of an action, which is moral precisely because it is inherently conformable to reason and nature, or immoral because it is at variance therewith. By what does reason gauge, however, whether an action or object is suited to the essential nature? St. Thomas gives the following explanation. Every agent, supposing that he is actually in possession of reason and freedom of will, acts for an end or purpose. The moving principle, the end, is thereby perceived and willed as something good. But a thing is an end only so far as it is a good, whose acquisition makes it worth one’s while to act. Goodness induces one to act. Goodness is, in final analysis, that which is in itself worth desiring and striving for. As cognition is directed to being, so the will is directed to goodness. And just as the intellect knows the thing so far as it has being, so the will lays hold of the thing, perceived as desirable or worth striving after, as good. All being is good. A being is a good so far as it appears suited to the essential nature. Now the supreme principles of speculative reason (the principle of contradiction, and so on, the immediately evident, axiomatic laws of thought) guide the intellect in its thinking. In the same way St. Thomas recognizes a supreme principle, a law, for the practical reason, for the will: good is to be done. The very same being which the theoretical reason knows as being and in which it apprehends truth, the agreement of knowledge with being, appears to the will and the practical reason as a good. That which is, also ought to be. Being, truth, and goodness are convertible. The law is truth; it wills what is good; and it presupposes knowledge of being.9
Good is to be done: such is the supreme commandment of the natural moral law. The highest and basic norm of the natural law in the narrow sense, then, may be stated thus: Justice is to be done. Yet this principle is altogether general. It needs still to be determined to what extent the object striven for by means of a concrete action is a true good. This is done more or less with the aid of a syllogism (which, of course, is not worked out in every case by concrete reasoning): Good is to be done; this action is good, it strives after a good; it is therefore to be performed. Good is that which corresponds to the essential nature. The being of a thing also reveals its purpose in the order of creation, and in its perfect fulfillment it is likewise the end or goal of its growth and development. The essential nature is thus the measure. What corresponds to it is good; what is contrary to it is bad. The measure of goodness, consequently, is the essential idea of a thing and the proportionateness thereto of actions and of other things. That is, “Good is to be done” means the same as “Realize your essential nature.” Moreover, since this essential nature issued from God’s creative will and wisdom in both its existence and its quiddity, the principle continues: “You thereby realize the will of God, which is truly manifested to you in the knowledge of your essential nature.” The same being is truth to the theoretical reason, and goodness to the practical reason.10
The train of thought thereupon widens. It follows that there are some actions which, because they correspond to the essential nature and its end, are in themselves good, moral, just; and that there are others which, because they are at variance therewith, are in themselves bad, immoral, unjust.11 At any rate, this is true on the assumption that both in God and in man the intellect, not the will, holds the primacy. For a natural moral law as an immutable basic norm, and the essential nature as a valid measure of what is moral and just, are possible only when this essence is itself unalterable. This presupposes, however, that the essential nature owes its idea, its quiddity, and its existence to the unchangeable essence of God Himself, of which they are reflections. “If, too, human nature is the immediate measure of moral goodness, it can be the norm of unalterable moral judgments only insofar as it itself embodies the idea of man as this rests from all eternity in the divine mind. But the ideas of things in the divine mind are, in their content, nothing else than the images through which God knows His own essence as imitable. This is true also of the idea of man.”12
The divine essence and, in one and the same act, the divine knowledge thereof and the creative will of God, likewise thereby informed in one and the same act, are (or rather, is) the basis for the essential nature and its immutability.