two [suggested] divisions of law: that of art, and that of custom. To these we may add a third group from the Timaeus [24 et seq.] and the Gorgias of this same Plato—the law of order or of natural propensity. Here, distinguishing a fourfold division of law, he gives to one part the name of natural law. We shall make some comments as to this division below (Chapter Three).5
For the present, we refer the expression ‘natural law’ not to that law which dwells in mankind, a division which we shall also discuss later, but rather to that which befits all things, in accordance with the inclination imparted to them by the Author of nature; for such appears to be Plato’s
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explanation of the term, although he admits that the law in question exists among men also, after a nobler fashion.
This third acceptation of law is therefore metaphorical, since things which lack reason are not, strictly speaking, susceptible to law, just as they are not capable of obedience. Accordingly, the efficacy of divine power, and the natural necessity resulting therefrom in this connexion, are metaphorically given the name of law. With this, indeed, the Scriptural phrase accords (Proverbs, Chap. viii [, v. 27]): ‘When with a certain law and compass he enclosed the depths’; as do, further on, the words [ibid., v. 29]: ‘[…] and set a law to the waters, that they should not pass their limits’. This sort of law is also referred to, in the term ‘measure’ in Job (Chap. xxxviii [, v. 5]): ‘Who hath laid the measure[s] thereof, if thou knowest?’ And we find below, the words: ‘Who shut up the sea with doors’ [ibid., v. 8]; ‘And I said: Hitherto thou shalt come’, &c. [ibid., v. 11].
Furthermore, it is in accordance with this acceptation that the term ‘law’ is wont to be applied to natural inclination; either because that inclination is the measure of the action toward which it impels one, or because it rises out of the law of the Creator. For this term ‘law’ is frequently applied both to the rule itself, and to the work or effect thereof, in so far as the latter conforms to the rule; just as the actual product of art is often called ‘art’. It is in this sense that one may interpret the following passages, from the Epistle to the Romans (Chap. ii [, v. 13]): ‘For not only6 the hearers [of the law are just before God,] but the doers of the law shall be justified’; (that is to say, [doers] of the work prescribed by the law;) and from John (Chap. vii [, v. 19]): ‘Did not Moses give you the law, and yet none of you keepeth7 the law’. However, in these passages, the word faciendum (doing or keeping) may also be taken in another sense as equivalent to the word observandum (observing).
3. Paul, too, may be interpreted according to this first acceptation, when, in the Epistle to the Romans (Chap. vii [, v. 23]), he speaks of the
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inclination of the sensitive appetite8 as ‘the law of the members’ and ‘a law of sin’, an inclination which St. Thomas (I.–II, qu. 90, art. 1, ad 1, and qu. 90 [qu. 91], art. 6) has called the lex fomitis9 (law of concupiscence).10 Furthermore, he there declares that this inordinate inclination of the fomes is called law, yet not formally, in the sense of law as a measure, but in a participatory sense, as one is wont to speak of that which is measured by law. Accordingly, St. Thomas holds, not that this inclination of the appetite comes of its very nature under the name of law, but that it does come under that name in so far as it is deprived of the rectitude of [its] original justice, owing to original sin, by operation of the punitive law of God. For in this sense, the inordinate nature of the fomes is not simply natural, but is a penalty of sin; and therefore, it is called ‘law’ in its capacity as an effect of divine law. Augustine (De Diversis Quaestionibus ad Simplicianum, Bk. I, qu. 1 [, no. 13]) seems to have held the same opinion, for he says: ‘This oppressive and weighty burden he calls law (lex), for the reason that it has been decreed and imposed by divine judgment through the law (ius) of punishment.’ Assuredly, this is to say that it was imposed by setting aside the [original] justice which endowed [the inclination] with the contrary quality of rectitude.
4. However, while the foregoing may be true, it would nevertheless seem that the inclination itself of the appetite, in so far as that inclination is purely natural, might be termed ‘law’ in the sense in which the natural inclination of water is so termed. For, in like manner, there would exist in man, in his purely natural state,11 this very law of the fomes, although
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it would not exist as a punishment for sin. Moreover, even to-day, this inclination of the fomes is apparently called law not only because it is an effect thereof, but also because it is (so to speak) a measure and rule of movements pertaining to the senses and has therefore been called by Paul ‘the law of the members’, as having dominion, in particular, over the members of the body. Thus it is that Augustine has said (De Genesi ad Litteram, Bk. V [Bk. IX], chap. x): ‘They have merited the operation in their members of that law which is opposed to the law of the mind.’12 So also is it that this law has been called the law of sin, not only because it is a result of sin, but also because it inclines thereto. In this sense, indeed, the law in question did not exist in Adam before the fall. For even though his sensitive appetite lacked not its natural propensity, it did not operate of itself, nor did it dominate in any way; neither was it a rule or measure of certain movements, but was, on the contrary, entirely subject to the law of the mind. However, for the matter of metaphorical locutions, the foregoing remarks will suffice.
5. The second13 acceptation of the word lex is a stricter one; for art is a work of the reason, and hence the rules that measure art may more properly be designated by the term lex. Accordingly, we are wont to distinguish among the military, and mercantile, and other laws; as St. Thomas has noted (I.–II, qu. 91, art. 6). The rules of correct speech, too, are customarily called the laws of grammar. And the same practice prevails in regard to other arts. Nevertheless, just as the rectitude of any art with respect to rational creatures is a relative rectitude, as St. Thomas remarks (ibid., qu. 56 [, art. 3]), even so the law of an art can be termed a law only in a relative sense.
Therefore, the name ‘law’ is properly applied, in an absolute sense, to that which pertains to moral conduct. And accordingly, we should narrow the description given by St. Thomas, so that it runs as follows: law is a certain measure of moral acts,14 in the sense that such acts are characterized
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by moral rectitude through their conformity to law, and by perversity, if they are out of harmony with law.
6. The true meaning of law. Hence, although unrighteous precepts or rules are frequently designated by the term ‘law’, as the saying in Isaias (Chap. xx [Chap. x, v. 1]) implies: ‘Woe to them that make wicked laws’, and as the words of Aristotle also imply (Nicomachean Ethics, Bk. IV, chap. i [Bk. V, chap. i, 1129 B]): ‘A law which is made at random is evil’15 (take, for example, the one which in popular speech is commonly called ‘the law of the world’, or ‘the law of the duel’, or some similar laws)—although, I repeat, this may be true—nevertheless, strictly and absolutely speaking, only that which is a measure of rectitude, viewed absolutely, and consequently only that which is a right and virtuous rule, can be called law. It is on this account that St. Thomas has said (I.–II, qu. 90, art. 1 [art. 2] and qu. 96, art. 4) that an evil precept is not law but iniquity; and St. Augustine has made the declaration, in the tractate On Free Will (Bk. I, chap. v): ‘That which is not just, does not seem to me to be [true] law (lex).’ Moreover, in his work On the City of God (Bk. XIX, chap. xxi), he lays down the same assertion, with regard to ius. Indeed, Cicero also has said (On Laws, Bk. II [, chap. v, § 11]) that law ought to be established to the end of promoting a just, quiet, and happy life; and that, therefore, those who are authors of unjust laws16 [so-called], have produced anything but [true] laws.
Plato amply confirms this assertion, in the Dialogue already cited.17 The reason supporting the view is also manifest in the light of what we have said above. For law is a measure of rectitude. But an unjust law is not a measure of the rectitude of human conduct. On the contrary, an action which conforms to it is unjust. Therefore, [such an unjust enactment] is
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not law, but partakes of the name of law by analogy (so to speak) in so far as it prescribes a certain mode of action in