Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that not every human law is derived from the natural law. For the Philosopher says (Ethic. v, 7) that "the legal just is that which originally was a matter of indifference." But those things which arise from the natural law are not matters of indifference. Therefore the enactments of human laws are not derived from the natural law.

Objection 2: Further, positive law is contrasted with natural law, as stated by Isidore (Etym. v, 4) and the Philosopher (Ethic. v, 7). But those things which flow as conclusions from the general principles of the natural law belong to the natural law, as stated above (Question 94, Article 4). Therefore that which is established by human law does not belong to the natural law.

Objection 3: Further, the law of nature is the same for all; since the Philosopher says (Ethic. v, 7) that "the natural just is that which is equally valid everywhere." If therefore human laws were derived from the natural law, it would follow that they too are the same for all: which is clearly false.

Objection 4: Further, it is possible to give a reason for things which are derived from the natural law. But "it is not possible to give the reason for all the legal enactments of the lawgivers," as the jurist says . Therefore not all human laws are derived from the natural law.

On the contrary, Tully says (Rhet. ii): "Things which emanated from nature and were approved by custom, were sanctioned by fear and reverence for the laws."

I answer that, As Augustine says (De Lib. Arb. i, 5) "that which is not just seems to be no law at all": wherefore the force of a law depends on the extent of its justice. Now in human affairs a thing is said to be just, from being right, according to the rule of reason. But the first rule of reason is the law of nature, as is clear from what has been stated above (Question 91, Article 2, ad 2). Consequently every human law has just so much of the nature of law, as it is derived from the law of nature. But if in any point it deflects from the law of nature, it is no longer a law but a perversion of law.

But it must be noted that something may be derived from the natural law in two ways: first, as a conclusion from premises, secondly, by way of determination of certain generalities. The first way is like to that by which, in sciences, demonstrated conclusions are drawn from the principles: while the second mode is likened to that whereby, in the arts, general forms are particularized as to details: thus the craftsman needs to determine the general form of a house to some particular shape. Some things are therefore derived from the general principles of the natural law, by way of conclusions; e.g. that "one must not kill" may be derived as a conclusion from the principle that "one should do harm to no man": while some are derived therefrom by way of determination; e.g. the law of nature has it that the evil-doer should be punished; but that he be punished in this or that way, is a determination of the law of nature.

Accordingly both modes of derivation are found in the human law. But those things which are derived in the first way, are contained in human law not as emanating therefrom exclusively, but have some force from the natural law also. But those things which are derived in the second way, have no other force than that of human law.

Reply to Objection 1: The Philosopher is speaking of those enactments which are by way of determination or specification of the precepts of the natural law.

Reply to Objection 2: This argument avails for those things that are derived from the natural law, by way of conclusions.

Reply to Objection 3: The general principles of the natural law cannot be applied to all men in the same way on account of the great variety of human affairs: and hence arises the diversity of positive laws among various people.

Reply to Objection 4: These words of the Jurist are to be understood as referring to decisions of rulers in determining particular points of the natural law: on which determinations the judgment of expert and prudent men is based as on its principles; in so far, to wit, as they see at once what is the best thing to decide.

Hence the Philosopher says (Ethic. vi, 11) that in such matters, "we ought to pay as much attention to the undemonstrated sayings and opinions of persons who surpass us in experience, age and prudence, as to their demonstrations."

Articulus 2

Argumentum 1

Ad secundum sic proceditur. Videtur quod non omnis lex humanitus posita a lege naturali derivetur.

Dicit enim philosophus, in V ethic., quod iustum legale est quod ex principio quidem nihil differt utrum sic vel aliter fiat.

Sed in his quae oriuntur ex lege naturali, differt utrum sic vel aliter fiat. Ergo ea quae sunt legibus humanis statuta, non omnia derivantur a lege naturae.

Argumentum 2

Praeterea, ius positivum dividitur contra ius naturale, ut patet per Isidorum, in libro etymol., et per philosophum, in V ethic..

Sed ea quae derivantur a principiis communibus legis naturae sicut conclusiones, pertinent ad legem naturae, ut supra dictum est.

Ergo ea quae sunt de lege humana, non derivantur a lege naturae.

Argumentum 3

Praeterea, lex naturae est eadem apud omnes, dicit enim philosophus, in V ethic., quod naturale iustum est quod ubique habet eandem potentiam.

Si igitur leges humanae a naturali lege derivarentur, sequeretur quod etiam ipsae essent eaedem apud omnes.

Quod patet esse falsum.

Argumentum 4

Praeterea, eorum quae a lege naturali derivantur, potest aliqua ratio assignari. Sed non omnium quae a maioribus lege statuta sunt, ratio reddi potest, ut iurisperitus dicit.

Ergo non omnes leges humanae derivantur a lege naturali.

Sed Contra

Sed contra est quod tullius dicit, in sua rhetor., res a natura profectas, et a consuetudine probatas, legum metus et religio sanxit.

Corpus

Respondeo dicendum quod, sicut Augustinus dicit, in I de Lib. Arb., non videtur esse lex, quae iusta non fuerit.

Unde inquantum habet de iustitia, intantum habet de virtute legis. In rebus autem humanis dicitur esse aliquid iustum ex eo quod est rectum secundum regulam rationis.

Rationis autem prima regula est lex naturae, ut ex supradictis patet.

Unde omnis lex humanitus posita intantum habet de ratione legis, inquantum a lege naturae derivatur. Si vero in aliquo, a lege naturali discordet, iam non erit lex sed legis corruptio.

Sed sciendum est quod a lege naturali dupliciter potest aliquid derivari, uno modo, sicut conclusiones ex principiis; alio modo, sicut determinationes quaedam aliquorum communium.

Primus quidem modus est similis ei quo in scientiis ex principiis conclusiones demonstrativae producuntur. Secundo vero modo simile est quod in artibus formae communes determinantur ad aliquid speciale, sicut artifex formam communem domus necesse est quod determinet ad hanc vel illam domus figuram. Derivantur ergo quaedam a principiis communibus legis naturae per modum conclusionum, sicut hoc quod est non esse occidendum, ut conclusio quaedam derivari potest ab eo quod est nulli esse malum faciendum. Quaedam vero per modum determinationis, sicut lex naturae habet quod ille qui peccat, puniatur; sed quod tali poena puniatur, hoc est quaedam determinatio legis naturae. Utraque igitur inveniuntur in lege humana posita. Sed ea quae sunt primi modi, continentur lege humana non tanquam sint solum lege posita, sed habent etiam aliquid vigoris ex lege naturali.

Sed ea quae sunt secundi modi, ex sola lege humana vigorem habent.

Ad 1

Ad primum ergo dicendum quod philosophus loquitur de illis quae sunt lege posita per determinationem vel specificationem quandam praeceptorum legis naturae.

Ad 2

Ad secundum dicendum quod ratio illa procedit de his quae derivantur a lege naturae tanquam conclusiones.

Ad 3

Ad tertium dicendum quod principia communia legis naturae non possunt eodem modo applicari omnibus, propter multam varietatem rerum humanarum. Et exinde provenit diversitas legis positivae apud diversos.

Ad 4

Ad quartum dicendum quod verbum illud iurisperiti intelligendum est in his quae sunt introducta a maioribus circa particulares determinationes legis naturalis; ad quas quidem determinationes se habet expertorum et prudentum iudicium sicut ad quaedam principia; inquantum scilicet statim vident quid congruentius sit particulariter determinari.

Unde philosophus dicit, in VI ethic., quod in talibus oportet attendere expertorum et seniorum vel prudentum indemonstrabilibus enuntiationibus et opinionibus, non minus quam demonstrationibus.