with the matter (or the potency or the possibility) and thus gives actuality to the individual. The archetype for Aristotle was human artistic activity: the architect who constructs a house according to the plan in his mind; the sculptor who molds a statue in accordance with his artistic conception; even organic nature which causes the plant to grow from the actualizing essential form that exists in the seed in an incorporeal manner. Aristotle wished to comprehend motion, development, becoming. To him, therefore, the essence, and the perfect expression of it in the individual, is also the telos, or end. The form is thus the efficient and the final cause at one and the same time. Applied to the domain of ethics, however, this means that pure being or the pure essential form is likewise the goal of becoming for the man who is to be fashioned by education into a good citizen. From the essential being results an oughtness for the individual man. In this way, from the content of the primary norm, “strive after the good,” arises the norm, “realize what is humanly good,” as it appears in the essential form of man. The supreme norm of morality is accordingly this: Realize your essential form, your nature. The natural is the ethical, and the essence is unchangeable.
But a criterion of actions is thereby established. Some actions correspond to nature, and hence are naturally good; others are repugnant to nature, and hence are naturally bad. This settled, Aristotle advances to the distinction between what is naturally just and what is legally just. Both are objects of justice. Justice, however, taken in the narrower sense (for in the wider sense the virtuous man is the just man purely and simply) and distinguished from morality, is directed to the other, to the fellow man, whether as equal (commutative justice) or as fellow member of the comprehensive polis-community (distributive and, in the behavior of the member with regard to the whole, legal justice). It finds expression in the natural law and in the positive law. The latter originates in the will of the lawmaker or in an act of an assembly; the natural law has its source in the essence of the just, in nature. That which is naturally right is therefore unalterable. It has everywhere the same force, quite apart from any positive law that may embody it. Statute or positive law varies with every people and at different times. Yet the natural law does not dwell in a region beyond the positive law. The natural law has to be realized in the positive law since the latter is the application of the universal idea of justice to the motley manifold of life. The immutable idea of right dwells in the changing positive law. All positive law is the more or less successful attempt to realize the natural law. For this reason the natural law, however imperfect may be its realization in the positive law, always retains its binding force. Natural law, i.e., the idea and purpose of law as such, has to be realized in every legal system. The natural law is thus the meaning of the positive law, its purpose and its ethically grounded norm.
Recognition of the fact that no system of positive law is altogether perfect brought Aristotle to the principle of equity. The law is a general norm, but the actual matters which it has to regulate issue from the diversity of practical life. Of necessity the positive law exhibits imperfections; it does not fit all cases. Equity thereupon requires that the individual case get its right, i.e., that the imperfection of the formal law be overcome by means of material justice, through the content of the natural law. Thus Aristotle already viewed the judge’s function of filling up gaps in the law as an attempt to apply the natural law—if indeed the positive law is rightly to bear the name of law at all. The gaps are consequently the gateways through which the natural law continually comes into play. In such cases the judge has to decide in accordance with the norm which the true lawgiver would himself apply if he were present; the true lawgiver of course is always assumed to will what is just. This is a celebrated formula which in these very words or in the form, “which he [the judge] would lay down as lawmaker,” still found its way into the great codifications of civil law undertaken in the nineteenth and twentieth centuries (e.g., the Austrian and Swiss Civil Codes).
Concerning the content of the natural law Aristotle had as little to say as Plato. This was in sharp contrast to the Sophists, who because of their political and socio-critical bias had admitted many reform proposals and demands into their natural law. The silence of Plato and Aristotle finds its explanation in their idea of the natural law: they set out from the conservative conviction that the positive law wishes to realize the natural law. Added to this was their strong belief in the excellence of the existing laws of the polis as well as in the conformity of such laws to the natural law. The city-state, its general welfare, and its happiness occupied so prominent a place in the ethical thinking of Plato and Aristotle—for whom indeed the idea of man achieves ultimate perfection in the good citizen—that they looked upon the existing laws as something holy. In contrast to the individualistic attack launched by the Sophists against them, the natural law of Plato and Aristotle served precisely to justify the existing laws and not merely as a basis for criticizing them, although the function of criticism was regarded as included in the idea of natural law. Furthermore, for Aristotle as for Plato the polis or city-state was the great pedagogue, against which, strictly speaking, no natural, subjective right of the citizen could be admitted. They acknowledged no goal of man that transcends the ideal polis. They remained state socialists. Their doctrine of natural law was from the political standpoint conservative, but it was based on metaphysics. With the effective discovery, through Christianity, of human personality and with the recognition of God’s intellect and will as the source of the natural moral law, rational thought would thenceforth be in a position to work its way through to the true natural law.
In the public squares of Athens and on the steps of its public buildings the wordy Sophists had once taught their rationalistic philosophy, their revolutionary natural-law doctrine. In the same places Socrates, the “lover of wisdom,” and Plato and Aristotle, following him, had risen up against the skepticism that was already making its appearance among the Sophists, a skepticism evoked by the doctrine of man as the measure of all things9 and by the resultant subjectivism in epistemology and ethics. This trio of thinkers had anchored anew in philosophy the natural law which at the hands of the Sophists had been threatening to decline into a mere rationalization of political interests.
With the disappearance of these intellectual giants from the scene, however, the Skeptics, the positivists of their day, began at once to hold forth in the same halls and gardens of the Academy at Athens. The senses, they taught, do not convey true knowledge but only illusion; even reason does not guarantee the truth and certitude of knowledge; certainly, then, truth cannot arise from the illusions of both the senses and reason. All laws, whether of art, speech, morality, or right, are arbitrary. They have their origin in mere agreement, and they vary with the change of the free will which establishes them. As no assertion is of more value than its opposite, so, too, no law is worth any more than its opposite. Likewise, since we cannot perceive the essence or nature of things and of man, a natural law is impossible.
Skepticism attained its highest point in the teaching of Carneades (cir. 215–125 B.C.), who for a long time was scholarch at Athens. About 155 B.C., in Rome, he directed his attacks against the natural-law doctrine of the Stoics, a contest which he had made the principal mission of his life. There he won fame through his pro-and-con method of demonstration, whereby he strove to heap ridicule upon the notion of justice. One of his most celebrated arguments was drawn from the borderline case known as “the plank of Carneades.” At a time of shipwreck two persons swim to a plank and grasp it simultaneously. But the plank can hold up and save only one of the two. In the light of this case what is right, and who has the right to the plank? Both and neither, he answered, in such a case of dire necessity and self-preservation. (Seventeen centuries later Suarez furnished the correct solution: the order of justice here terminates, and the order of charity governs the case.) Positivism in ethics and law reached its climax with Carneades, again in connection with the repudiation of objective knowledge of reality and essences and with the denial of metaphysics.
Stoicism prepared the way for the Christian natural law. It was founded in Greece as a school of philosophy by Zeno, who lived from about 340 to 265 B.C. It came to its full flowering in Rome in the imperial age. The great figures of Seneca and the emancipated slave Epictetus as well as the appealing personality of Emperor Marcus Aurelius there adorned the Stoic school. Cicero, however, was its great popularizer, and the wealth of Stoic thought was handed down to the medieval world mainly in his writings.
