Chapter VII: The Law of Nature in the Middle Ages

When the succession of Roman jurists as a professional class came to an end, and the level of culture in the whole community declined in Western Europe after the destruction of imperial power in the Western provinces, the ecclesiastics, among some of whom a tincture of legal knowledge remained, naturally identified the law of Nature with the law of God. We have this clearly expressed in the passages from Isidore of Seville (who wrote early in the seventh century) which obtained immense circulation and influence by being incorporated (in the twelfth century) in the introductory paragraphs of the _Decretum_ of Gratian, the oldest part of the collected Canon Law. Isidore says[71]: ‘All laws are either divine or human. The divine rest upon Nature, the human upon custom; and the latter accordingly differ among themselves, because different laws have pleased different nations.’ Gratian himself, in the paragraph preceding, says: ‘Mankind is ruled by two things, natural law and customs. Natural Law is that which is contained in the law and the gospel, whereby every one is commanded to do to another that which he would have done to himself.’ This identification, already suggested by the Stoics and by some of the Roman jurists themselves[72], was inevitable as soon as Christianity appeared on the scene. St. Paul, as we have seen, recognized a law written by God on men’s hearts; St. Augustine speaks of the Eternal Law which governs the City of God. Nature—that is to say the Power that rules all things, the Force that is in all things—is, to a Christian, God; as St. Chrysostom says, ‘when I speak of Nature I mean God, for it is He who has made the world[73].’ The idea receives its final expression in Dante’s identification of the Divine Love with the Force that pervades the universe—

‘L’Amor che muove il sol e le altre stelle.’

Accordingly the scholastic philosophers posit a Law of Nature as being the work of God. St. Thomas of Aquinum introduces a useful distinction which exercised an enduring influence. The Eternal Law which governs all things is the expression of the Reason of God, the supreme Lawgiver. That part of it which is not revealed, but is made known to man by his own reason, may fitly be called Natural Law, as being the outcome of human reason, itself created and directed by the Divine Reason. Thus the sharing in the Eternal Law by a rational creature is Natural Law[74]. And so Suarez says that the Law of Nature is in God the Eternal Law, and in men is the light which carries this eternal law into their souls, being applied by conscience.

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Footnote 71:

‘Omnes leges aut divinae sunt aut humanae. Divinae natura, humanae
moribus constant, ideoque hae discrepant, quoniam aliae aliis gentibus
placent. Fas lex divina est: ius lex humana. Transire per agrum
alienum fas est, ius non est.’—_Dist. Prima_, c. i. ‘Humanum genus
duobus regitur, naturali videlicet iure et moribus. Ius naturale est
quod in lege et evangelio continetur, quo quisque iubetur alii facere
quod sibi vult fieri et prohibetur alii inferre, quod sibi nolit
fieri. Unde Christus in Evangelio “Omnia quaecunque vultis ut faciant
vobis homines, et vos eadem facite illis. Haec est enim lex et
prophetae.”’ Here the Sermon on the Mount is taken as stating the Law
of Nature.

Footnote 72:

Cf. the citation by Marcian, in _Dig._ i. 3. 2, of the dictum of
Demosthenes (_Adv. Aristog._ p. 774) νόμος εὕρημα καὶ δῶρον θεοῦ; and
Justinian’s _Institutes_, i. 2, § 11 ‘Naturalia iura, quae apud omnes
gentes peraeque servantur, divina quadam providentia semper firma
atque immutabilia permanent.’

Footnote 73:

ὅταν εἴπω τὴν φύσιν, Θεὸν λέγω, ὁ γὰρ τὴν φύσιν δημιουργήσας αὐτὸς
ἔστιν.

Footnote 74:

_Summa Theologiae_, prima secundae, Q. xciv. 2.

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I cannot here pursue an inquiry into the treatment of these notions by the scholastic theologians and philosophers, nor by their successors who belong to the school of the Catholic Renaissance in the sixteenth century, for the subject is a vast one. Neither have I space to deal with the students and teachers of the Roman Law during the thirteenth, fourteenth, and fifteenth centuries, of whom however it may be said that Natural Law has in their pages a less definite character than it bore to the ancient jurists, and is more coloured by that ethical atmosphere which they found in the treatment of it by Cicero and Aristotle and by such ecclesiastical authorities as Gratian and St. Thomas. It was during these centuries less widely and effectively used in the sphere of pure law than in those of speculation and actual political controversy. In these latter spheres it played a great part, being appealed to by the advocates as well of imperial as of papal pretensions, the one side claiming its support for the temporal, the other side for the spiritual potentate. All admitted that it stood above both these powers, and some maintained that where either power transgressed it, he might be lawfully resisted by his subjects[75]. Now and then princes put it forward as a ground for legislation. Philip the Fair of France, proposing to liberate serfs, says (A.D. 1311) that ‘every human creature formed in the image of Our Lord ought by natural law to be free.’ Now and then a jurist specifies matters in which it limits the legislator’s power, as Baldus says, neither Emperor nor Pope could validly authorize the taking of usury[76]. But one can hardly say that the idea emerges as an independently formative power in the growth either of the Canon Law in Europe, or of the law of Islam in the East, for the obvious reason that ecclesiastical systems do not need it. The Bible in Christendom, the Koran where Islam ruled, supplied all the philosophical basis and all such indications of the Divine Will as were needed to give law a moral character. So, although the term is indeed frequently used by mediaeval writers of all types, it is generally used with a theological or ethical bearing. Nature, except in such a sense as was given to it by St. Paul, or in such expressions as were sanctioned by Aristotle or by the texts of the jurists, would have sounded strange, and might have savoured of heterodoxy. As the Chancellor says in the second part of Goethe’s _Faust_—

‘Natur und Geist! so spricht man nicht zu Christen:
Desshalb verbrennt man Atheisten.’

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Footnote 75:

On this subject see the authorities collected and luminously expounded
by Professor Dr. Gierke in his _Johannes Althusius_, chap. vi.

Footnote 76:

Gierke, _ut supra_. Baldus and other jurists declare that the Emperor
‘tenetur ratione naturali, cum ius naturae sit potentius principatu,’
and one goes so far as to hold him to be also bound by _ius gentium_.
See Arthur Duck, _De Usu et Authoritate Iuris Civilis_, bk. i. chap.
iii, § 12.

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Yet throughout this period the place which this conception holds and the function which it discharges in the world of thought, if not in that of practice, are of high import. It is an assertion of the supremacy of the eternal principles of morality, of the duty of princes to obey those principles, of the right of citizens to defend them, if need be even by rebellion or tyrannicide. It proclaims the responsibility to God of all power, whether spiritual or temporal, and the indestructible rights of the individual human being. Finding in the Divine Justice the ultimate source of all law, it imposes a restraint upon the force which positive law has at its command, and sets limits to the validity of positive laws themselves. Whether or no the individualistic spirit of the Teutonic races contributed to this remarkable change from the attitude of the Roman lawyers is a question I will not attempt to discuss. But it is clear that the influence of Christian teaching had, even under a dominant and persecuting ecclesiastical system, stimulated the vindication in the name of Natural Law of principles which are the foundation both of civil and of religious liberty.