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. “That God of necessity enacts and cannot alter that law which we call the natural law comes merely from the fact that His will cannot do away with His most perfect essence, that God cannot be at variance with Himself and cannot, as the Apostle says, deny Himself” (Kleutgen). This is the fundamental reason for rejecting moral and legal positivism. The will is not the law; on the contrary, it can only be right law when it is guided even in God by reason and intellect. “But to say that justice depends upon mere will is to say that the divine will does not proceed according to the order of wisdom, which is blasphemy.”13
Good is to be done, evil is to be avoided: this basic norm of the natural moral law has thus the character of an axiom. The real question, however, is that of its application to the concrete case. As another expression for the first rule of the lex naturalis, as general principles known to all, St. Thomas mentions love of God and of one’s neighbor. Man knows other principles only through deductive reason, yet not with altogether unerring certitude. For, in contrast with the speculative reason, the knowledge of the practical reason is more severely menaced in its clarity by the passions, by sinful inclinations. These conclusions from principles are for St. Thomas, as he explains in a searching inquiry into the problem, identical with the Decalogue, or Ten Commandments. The Decalogue contains the most essential conclusions for the simple reason that its precepts do not result from an arbitrary arrangement made by God, but from the fundamental distinction of good and evil. The first table of the Decalogue (first three Commandments) embraces the moral norms that relate to the worship of God; these required a special promulgation, in the view of St. Thomas, because they are not so evident as the laws found in the second table. The latter (the last seven Commandments), which are derived from the mutual relations among men and from the essence and goal of human nature, are, on the other hand, known more readily and with greater evidence. Human society in all its groupings ought to be built up in accordance with justice.
The Decalogue (second table) presents the norms that follow from the essential relationships which in their turn are given in the essential nature of man as a rational, free, and social being. These precepts, as norms with a material content, protect the family and parental authority (Fourth Commandment), human life (Fifth Commandment), the person in the capital sense of husband and wife (Sixth Commandment), property (Seventh Commandment), and honor (Eighth Commandment); lastly they forbid (Ninth and Tenth Commandments) inordinate, illicit longing for those goods which are especially exposed to covetousness and, moreover, whose wrongful appropriation does not arouse that natural abhorrence which infractions of the Fourth, Fifth, and Eighth Commandments do.14 St. Thomas regards it as self-evident that the further deductions from these conclusions do not possess the same evidence, since they necessarily lose, in favor of particular prescriptions, the universal character required for evidence. Furthermore, they are not so unmistakably recognizable that errors about them may not arise in the minds of individuals as well as among groups.15 Moreover, they do not share in the prerogative of immutability enjoyed by the principia communissima as well as by the conclusions which make up the contents of the Decalogue.
For instance, from the nature of the legal institution, from the agreement with reason and from the right of property, which in the general sense is protected by the Seventh Commandment, it follows that goods held in trust should be restored to their owner. Nevertheless, as St. Thomas points out, such goods may be withheld from their owner in case they are to be used for treasonable purposes.16 Here the further conclusion does not hold good, although the universal norm of acting according to reason, the suum cuique, continues absolutely to govern the case. Some “matters cannot be the subject of judgment without much consideration of the various circumstances. Not all are able to do this carefully, but only those who are wise.”17 “In the very application of the universal principle to some particular case a mistake can occur through an inadequate or false deduction, or by reason of some false assumption”;18 and in the matter of its secondary precepts, “the natural law can be blotted out from the human heart, either by evil persuasions … or by vicious customs and corrupt habits.”19 Therein, moreover, practical reason differs significantly from theoretical reason, which is less subject to such disturbing influences.
This does not, then, mean merely that there is in St. Thomas no trace whatever of the extravagances of the rationalistic natural law current in the seventeenth and eighteenth centuries, since according to him only the Decalogue belongs to the contents of the natural law. It further means that the lex naturalis or ius naturale does not render positive laws superfluous, but actually calls for them. St. Thomas gives scarcely any attention to the doctrine of a state of nature,
