a ruler or upon the decree of a multitude, but upon nature, i.e., upon innate ideas (non scripta sed nata lex).10 Cicero (106–43 B.C.) was the interpreter and transmitter of the Stoic doctrine of natural law. The LEX NATA, the law within us, he regards as the foundation of law in general. It is not to be gathered, as a general concept by way of abstraction, from the law of the Twelve Tables or from the praetor’s edict—that is, from the positive law—but EX INTIMA PHILOSOPHIA. Since it is identical with right reason, it is universally valid, unchangeable and incapable of being abrogated; for its author is the divine reason itself—taken, of course, in a pantheistic, impersonal sense. It is also called eternal law. Cicero could thus write: “If the principles of Justice were founded on the decrees of peoples, the edicts of princes, or the decisions of judges, then Justice would sanction robbery and adultery and forgery of wills, in case these acts were approved by the votes or decrees of the populace. But if so great a power belongs to the decisions and decrees of fools that the laws of Nature can be changed by their votes, then why do they not ordain that what is bad and baneful shall be considered good and salutary? Or, if a law can make Justice out of Injustice, can it not also make good out of bad? But in fact we can perceive the difference between good laws and bad by referring them to no other standard than Nature: indeed, it is not merely Justice and Injustice which are distinguished by Nature, but also and without exception things which are honourable and dishonourable. For since an intelligence common to us all makes things known to us and formulates them in our minds, honourable actions are ascribed by us to virtue, and dishonourable actions to vice; and only a madman would conclude that these judgments are matters of opinion, and not fixed by Nature.”11 Time and again the gifted rhetorician contrasts in this manner the law of nature, as the measure and inner source of validity, with the positive law, which to him is a shadow and reflected image of the true law.12
Epictetus (cir. A.D. 60–110) likewise called attention to the diversity of the laws that prevail at various times and among different peoples. He taught that the test of whether or not a law accords with nature consists in its agreement or non-agreement with reason. The laws that upheld slavery he called laws of the dead, an abysmal crime. Seneca (d. A.D. 65), in the teeth of the prevailing institution of slavery, gladiatorial combats, and shows featuring the throwing of human beings to beasts, voiced this magnificent sentiment apropos of human dignity: homo sacra res homini.13 What were originally Sophist doctrines were gaining fresh currency: the dignity of the human being and the natural-law basis of freedom and equality. Slaves, too, are men, blood relations and brethren. Like freemen, they are God’s own children, members of a great community. The city-state has thus lost its power, and with it has disappeared the differentiation of mankind into Greeks and barbarians, into freemen and slaves. “All that you behold, that which comprises both god and man, is one—we are the parts of one great body. Nature produced us related to one another since she created us from the same source and to the same end. She engendered in us mutual affection, and made us prone to friendships. She established fairness and justice.”14 A magnificent statement of the civitas maxima, the great society or world state, and of its fundamental law, the natural law! As Marcus Aurelius expressed it: “My city and country, so far as I am Antoninus, is Rome, but so far as I am a man, it is the world.”15
These Stoic views are singularly impressive in an environment that was replete with despotic brutality and contempt for man, with excesses and misuse of power, with a many-sided suppression of freedom. It is of far greater consequence, however, that they penetrated into Roman law, led to a recognition of the individual in private law, and elevated to the dignity of natural law the more liberal principles of the ius gentium which had developed out of the law of foreigners. Above all, they brought to the original tribalism and formalism of Roman law a universalism which fitted it “to survive, as a world law, the life of the nation in which it had originated” (Puchta). Among the later Stoics, too, we find the doctrine of a state of nature, a happy condition of mankind in which all the Stoic ideals of right and freedom had been realized and where the pure natural law had consequently been in force.16 The status civilis, on the other hand, with slavery organized and protected by the positive law, was looked upon as a state of affairs in which the natural law, though continuing in force, no longer holds sole sway.
In Stoicism, then, the mind of the ancient world had come to embrace whatever views Heraclitus, Plato, Aristotle, and the moderate Sophists had held regarding the natural law—all that they had taught touching the lex aeterna, recta ratio, lex naturalis, ius naturale, as well as concerning the connections of these with positive law and their evaluating force in relation to it. It thus preserved the “seeds of the Logos,” and it found the literary forms or word vessels into which the Christian spirit was to pour its own ideas, which eventually matured into a new, yet related, doctrine of natural law.
Under the influence of Stoic philosophy the doctrine of the natural law passed into Roman law. The great jurists of the golden age of Roman law were for the most part also philosophers. Through the medium of eclectic Stoicism they were acquainted with Aristotle’s teaching on justice and with Zeno’s work On the Laws; especially, however, they were familiar with the writings of Cicero, the popular philosopher of Stoicism. Besides, the forensic orators were interested in philosophy in their pleadings at the bar. Among these Cicero held first place, but there were also Q. Mucius Scaevola, Calpurnius, and Rutilius, as Cicero himself informs us. This philosophical bent is likewise evidenced by the frequency with which the jurists cite the philosophers. Gaius, for example, quotes Aristotle and Xenophon; Ulpian and Celsus quote Cicero; Paulus mentions Graeci in general. The peculiar function of the jurists, “responding,” i.e., imparting legal information and counsel to the judges and litigants alike,17 involved for the jurists this deeper kind of intellectual labor. Thus Stoic philosophy may with considerable justice be called the mother of Roman jurisprudence. The latter, to keep up the metaphor, sucked in the doctrine of the ius naturale with its mother’s milk.
Down to the time of Cicero neither science nor the natural-law doctrine had exercised any practical influence on Roman law. Then, however, theory broke in along a broad front. For Gaius, Paulus, and Marcian the ius naturae is a norm which from the very beginning lies forever imbedded in the nature of things; since it also reveals itself in things, it can be discovered in them. The Stoic idea of an eternal law of the order of the universe was present to their minds. This law emanates from the logos, which in turn is itself the law of things. The logos, moreover, expresses itself conceptually in the nature of things, and it destines them for harmony with the universe. Hence wherever two beings, whether man and thing or two men, find themselves related to each other, a rule covering what is naturally and essentially conformable to this relationship is present in the law of the logos—and is at the same time expressed a priori in the very nature of the correlates. A law rules as an ordering force in the natura rerum, in the world of both irrational and rational creatures.
This became of practical importance as a norm for positive legislation and for the deciding of cases for which the positive law contained no norm. But the natural law especially became the magic formula whereby the jurists in their responsa replaced the ancient law, which had by then become inadequate, with new law introduced under the concepts of lex naturae and aequitas. This they accomplished by means of the edict of the magistrates who were under their influence as well as through the imperial constitutions. In addition, the new law had in its favor the splendor of inherent truth or reason, the charm of simple conformity with nature, and the grandeur of transcending peoples and ages. But to the jurists aequitas was the echo of the lex naturae, the command of an inner voice through which speaks the ratio of the natura rerum immanent in things. Aequitas is the legal conscience which speaks even when a positive norm is at hand, for it is the “meaning” of the positive law. Adjudication, or applying the law, is not a logical and automatic process of subsuming under a general norm: it is interpretation in the light of aequitas.
As material contents of the law of nature the jurists designated such things as the rules touching kinship (marriage—family), good faith, adjustment or weighing of interests (suum cuique), the real meaning of the actual will of the legal subject as opposed to the formalism of the law governing expression of will. To these may be added the original freedom and equality of all men, and the right of self-defense (vim vi repellere).
Furthermore, the jurists, e.g., Paulus, Ulpian, and