1. NATURAL LAW AND REASON
AMONG INTELLECTUALS WHO CONSIDER themselves “scientific,” the phrase “the nature of man” apt to have the effect of a red flag on a bull. “Man has no nature!” is the modern rallying cry; and typical of the sentiment of political philosophers today was the assertion of a distinguished political theorist some years ago before a meeting of the American Political Science Association that “man’s nature” is a purely theological concept that must be dismissed from any scientific discussion.
In the controversy over man’s nature, and over the broader and more controversial concept of “natural law,” both sides have repeatedly proclaimed that natural law and theology are inextricably intertwined. As a result, many champions of natural law, in scientific or philosophic circles, have gravely weakened their case by implying that rational, philosophical methods alone cannot establish such law: that theological faith is necessary to maintain the concept. On the other hand, the opponents of natural law have gleefully agreed; since faith in the supernatural is deemed necessary to belief in natural law, the latter concept must be tossed out of scientific, secular discourse, and be consigned to the arcane sphere of the divine studies. In consequence, the idea of a natural law founded on reason and rational inquiry has been virtually lost.
The believer in a rationally established natural law must, then, face the hostility of both camps: the one group sensing in this position an antagonism toward religion; and the other group suspecting that God and mysticism are being slipped in by the back door. To the first group, it must be said that they are reflecting an extreme Augustinian position which held that faith rather than reason was the only legitimate tool for investigating man’s nature and man’s proper ends. In short, in this fideist tradition, theology had completely displaced philosophy.  The Thomist tradition, on the contrary, was precisely the opposite: vindicating the independence of philosophy from theology and proclaiming the ability of man’s reason to understand and arrive at the laws, physical and ethical, of the natural order. If belief in a systematic order of natural laws open to discovery by man’s reason is per se anti-religious, then anti-religious also were St. Thomas and the later Scholastics, as well as the devout Protestant jurist Hugo Grotius. The statement that there is an order of natural law, in short, leaves open the problem of whether or not God has created that order; and the assertion of the viability of man’s reason to discover the natural order leaves open the question of whether or not that reason was given to man by God. The assertion of an order of natural laws discoverable by reason is, by itself, neither pro- nor anti-religious.
Because this position is startling to most people today let us investigate this Thomistic position a little further. The statement of absolute independence of natural law from the question of the existence of God was implicit rather than flatly asserted in St. Thomas himself; but like so many implications of Thomism, it was brought forth by Suarez and the other brilliant Spanish Scholastics of the late sixteenth century. The Jesuit Suarez pointed out that many Scholastics had taken the position that the natural law of ethics, the law of what is good and bad for man, does not depend upon God’s will. Indeed, some of the Scholastics had gone so far as to say that:
even though God did not exist, or did not make use of His reason, or did not judge rightly of things, if there is in man such a dictate of right reason to guide him, it would have had the same nature of law as it now has.
Or, as a modem Thomist philosopher declares:
If the word “natural” means anything at all, it refers to the nature of a man, and when used with “law,” “natural” must refer to an ordering that is manifested in the inclinations of a man’s nature and to nothing else. Hence, taken in itself, there is nothing religious or theological in the “Natural Law” of Aquinas.
Dutch Protestant jurist Hugo Grotius declared, in his De Iure Belli ac Pacis (1625):
What we have been saying would have a degree of validity even if we should concede that which cannot be conceded without the utmost wickedness, that there is no God.
Measureless as is the power of God, nevertheless it can be said that there are certain things over which that power does not extend. . . . Just as even God cannot cause that two times two should not make four, so He cannot cause that which is intrinsically evil be not evil.
D’Entrèves concludes that:
[Grotius’s] definition of natural law has nothing revolutionary. When he maintains that natural law is that body of rules which Man is able to discover by the use of his reason, he does nothing but restate the Scholastic notion of a rational foundation of ethics. Indeed, his aim is rather to restore that notion which had been shaken by the extreme Augustinianism of certain Protestant currents of thought. When he declares that these rules are valid in themselves, independently of the fact that God willed them, he repeats an assertion which had already been made by some of the schoolmen.
Grotius’s aim, d’Entrèves adds, “was to construct a system of laws which would carry conviction in an age in which theological controversy was gradually losing the power to do so.” Grotius and his juristic successors—Pufendorf, Burlamaqui, and Vattel—proceeded to elaborate this independent body of natural laws in a purely secular context, in accordance with their own particular interests, which were not, in contrast to the Schoolmen, primarily theological. Indeed, even the eighteenth-century rationalists, in many ways dedicated enemies of the Scholastics, were profoundly influenced in their very rationalism by the Scholastic tradition.
Thus, let there be no mistake: in the Thomistic tradition, natural law is ethical as well as physical law; and the instrument by which man apprehends such law is his reason-not faith, or intuition, or grace, revelation, or anything else. In the contemporary atmosphere of sharp dichotomy between natural law and reason—and especially amid the irrationalist sentiments of “conservative” thought—this cannot be underscored too often. Hence, St. Thomas Aquinas, in the words of the eminent historian of philosophy Father Copleston, “emphasized the place and function of reason in moral conduct. He [Aquinas] shared with Aristotle the view that it is the possession of reason which distinguished man from the animals” and which “enables him to act deliberately in view of the consciously apprehended end and raises him above the level of purely instinctive behavior.”
Aquinas, then, realized that men always act purposively, but also went beyond this to argue that ends can also be apprehended by reason as either objectively good or bad for man. For Aquinas, then, in the words of Copleston, “there is therefore room for the concept of ‘right reason,’ reason directing man’s acts to the attainment of the objective good for man.” Moral conduct is therefore conduct in accord with right reason: “If it is said that moral conduct is rational conduct, what is meant is that it is conduct in accordance with right reason, reason apprehending the objective good for man and dictating the means to its attainment.”
In natural-law philosophy, then, reason is not bound, as it is in modern post-Humean philosophy, to be a mere slave to the passions, confined to cranking out the discovery of the means to arbitrarily chosen ends. For the ends themselves are selected by the use of reason; and “right reason” dictates to man his proper ends as well as the means for their attainment. For the Thomist or natural-law theorist, the general law of morality for man is a special case of the system of natural law governing all entities of the world, each with its own nature and its own ends. “For him the moral law . . . is a special case of the general principles that all finite things move toward their ends by the development of their potentialities.” And here we come to a vital difference between inanimate or even non-human living creatures, and man himself; for the former are compelled to proceed in accordance with the ends dictated by their natures, whereas man, “the rational animal,” possesses reason to discover such ends and the free will to choose.
Which doctrine, natural law or those of its critics, is to be considered truly rational was answered incisively by the late Leo Straus, in the course of a penetrating critique of the value-relativism in political theory of Professor Arnold Brecht. For, in contrast to natural law,
positivistic social science . . . is characterized by the abandonment of reason or the flight from reason. . . .
According to the positivistic interpretation of relativism which prevails in present-day social science . . . reason can tell us which means are conducive to which ends; it cannot tell us which attainable ends are to be preferred to other attainable ends. Reason cannot tell us that we ought to choose attainable ends; if someone ‘loves him who desires the impossible,’ reason may tell him that he acts irrationally, but it cannot tell him that he ought to act rationally, or that acting irrationally is acting badly or basely. If rational conduct consists in choosing the right means for the right end, relativism teaches in effect that rational conduct is impossible.
Finally, the unique place of reason in natural-law philosophy has been affirmed by the modern Thomistic philosopher, the late Father John Toohey. Toohey defined sound philosophy as follows: “Philosophy, in the sense in which the word is used when scholasticism is contrasted with other philosophies, is an attempt on the part of man’s unaided reason to give a fundamental explanation of the nature of things.”
The political theorist was the late Hannah Arendt. For a typical criticism of natural law by a legal Positivist, see Hans Kelsen, General Theory of Law and State (New York: Russell and Russell, 1961), pp. 8ff.
And yet, Black’s Law Dictionary defines the natural law in a purely rationalistic and non-theological manner:
Jus Naturale, the natural law, or law of nature; law, or legal principles, supposed to be discoverable by the light of nature or abstract reasoning, or to be taught by nature to all nations and men alike, or law supposed to govern men and peoples in a state of nature, i.e., in advance of organized governments or enacted laws (3rd ed., p. 1044).
Professor Patterson, in Jurisprudence: Men and Ideas of the Law (Brooklyn: Foundation Press, 1953), p. 333, defines the natural law cogently and concisely as:
Principles of human conduct that are discoverable by “reason” from the basic inclinations of human nature, and that are absolute, immutable and of universal validity for all times and places. This is the basic conception of scholastic natural law . . . and most natural law philosophers.
Supporters of theological ethics nowadays typically strongly oppose the concept of natural law. See the discussion of casuistry by the neo-orthodox Protestant theologian Karl Barth, Church Dogmatics 3,4 (Edinburgh: T. and T. Clark, 1961), pp. 7ff.
For a discussion of the role of reason in the philosophy of Aquinas, see Etienne Gilson, The Christian Philosophy of St. Thomas Aquinas (New York: Random House, 1956). An important analysis of Thomistic natural law theory is Germain Grisez, “The First Principle of Practical Reason,” in Anthony ed., Aquinas: A Collection of Critical Essays (New York: Anchor Books, 1969), pp. 340–82. For a history of medieval natural law, see Odon Lottin, Psychologie et morale aux xiie et xiiie siècles, 6 vols. (Louvain, 1942-1960).
From Franciscus Suarez, De Legibus ac Deo Legislatore (1619), lib. II, Cap. vi. Suarez also noted that many Scholastics “seem therefore logically to admit that natural law does not proceed from God as a lawgiver, for it is not dependent on God’s will.” Quoted in A. P. d’Entrèves, Natural Law (London: Hutchinson University Library, 1951), p. 71.
Thomas E. Davitt, S.J., “St. Thomas Aquinas and the Natural Law,” in Arthur L. Hading, ed., Origins of the Natural Law Tradition (Dallas, Tex.: Southern Methodist University Press, 1954), p. 39. Also see Brendan F. Brown, ed., The Natural Law Reader (New York: Oceana Pubs., 1960), pp. 1014.
Quoted in d’Entrèves, Natural Law, pp. 52–53. See also Otto Gierke, Natural Law and the Theory of Society, 1500 to 1800 (Boston: Beacon Press, 1957), pp. 98–99.
D’Entrèves, Natural Law, pp. 51-52. Also see A.H. Chroust, “Hugo Grotius and the Scholastic Natural Law Tradition,” The New Scholasticism (1943), and Frederick C. Copleston, S.J., A History of Philosophy (Westminster, Md.: Newman Press, 1959), 2, pp. 330f. On the neglected influence of the Spanish Scholastic Suarez on modern philosophers, see Jose Ferrater Mora, “Suarez and Modem Philosophy,” Journal of the History of Ideas (October 1953): 528–47.
See Gierke, Natural Law and the Theory of Society, p. 289. Also see Herbert Spencer, An Autobiography (New York: D. Appleton, 1904), vol. 1,p. 415.
Thus, see Carl L. Becker, The Heavenly City of the Eighteenth-Century Philosophers (New Haven, Conn.: Yale University Press, 1957), p. 8.
The late realist philosopher John Wild, in his important article, “Natural Law and Modern Ethical Theory,” Ethics (October 1952), states:
Realistic [natural law] ethics is now often dismissed as theological and authoritarian in character. But this is a misunderstanding. Its ablest representatives, from Plato and Aristotle to Grotius, have defended it on the basis of empirical evidence alone without any appeal to supernatural authority (p. 2, and pp. 1–13).
Also see the denial of the existence of such a thing as “Christian philosophy” any more than “Christian hats and shoes” by the Catholic social philosopher Orestes Brownson. Thomas T. McAvoy, C.S.C., “Orestes A. Brownson and Archbishop John Hughes in 1860,” Review of Politics (January 1962): 29.
Frederick C. Copleston, S.J., Aquinas (London: Penguin Books, 1955), p. 204.
Ibid., pp. 204–05.
Ibid., p. 212.
 Thus Copleston:
Inanimate bodies act in certain ways precisely because they are what they are, and they cannot act otherwise; they cannot perform actions which are contrary to their nature. And animals are governed by instinct. In fine, all creatures below man participate unconsciously in the eternal law, which is reflected in their natural tendencies, and they do not possess the freedom which is required in order to be able to act in a manner incompatible with this law. It is therefore essential that he [man] should know the eternal law in so far as it concerns himself. Yet, how can he know it? He cannot read, as it were, the mind of God . . . [but] he can discern the fundamental tendencies and needs of his nature, and by reflecting on them he can come to a knowledge of the natural moral law. . . . Every man possesses . . . the light of reason whereby he can reflect . . . and promulgate to himself the natural law, which is the totality of the universal precepts or dictates of right reason concerning the good which is to be pursued and the evil which is to be shunned (Ibid., pp. 213–14).
Leo Strauss, “Relativism,” in H. Schoeck and J.W. Wiggins, eds., Relativism and the Study of Man (Princeton, N.J.: D. Van Nostrand, 1961), pp. 144–435. For a devastating critique of an attempt by a relativistic political scientist to present a “value-free” case for freedom and the self-development of the person, see Walter Berns, “The Behavioral Sciences and the Study of Political Things: The Case of Christian Bay’s The Structure of Freedom,” American Political Science Review (September 1961): 550–59.
Toohey adds that “scholastic philosophy is the philosophy which teaches the certitude of human knowledge acquired by means of sense experience, testimony, reflection, and reasoning.” John J. Toohey, S.J., Notes on Epistemology (Washington, D.C.: Georgetown University, 1952), pp. 111–12.