Introduction

In the year 38 A.D., the Roman Emperor Caligula sought to restock the imperial treasuries by instituting tax laws that carried severe financial penalties for anyone who violated the newly minted statutes. To ensure the financial success of his venture, Caligula initially refused to make the laws known, but still enforced them and collected the ensuing hefty fines. When enough bewildered citizens protested, Caligula had the laws inscribed in tiny letters on a tablet suspended high above the ground on a pillar. Suetonius describes the ordeal as follows:

When taxes of this kind had been proclaimed, but not published in writing, inasmuch as many offences were committed through ignorance of the letter of the law, he at last, on the urgent demand of the people, had the law posted up, but in a very narrow place and in excessively small letters, to prevent the making of a copy.{1}

Caligula’s legislative ruse and the Roman people’s indignant response illuminate essential questions regarding the institution of a legal order. How can a law function as law unless it is made known to its citizens? Is a legislator required, by some source of normativity deeper than the positive law itself, to publicize the laws of the polity in order for them to be binding? Is there some kind of natural injustice intrinsic to Caligula’s scheme?

Caligula’s racket enables us to see that there are what we might call natural necessities, and thus natural excellences, pertaining to the very being of things. In this case, these natural necessities and excellences pertain to law as a way of organizing and directing the life of a political society. Given what an authoritative rule for a society is, what money and fines are, and what human beings are who must respond to the one by paying or avoiding the other, we can quickly understand that the law must be publicly manifest and available in order for the legal system to function. Even if the positive law were to remain silent about the necessity of promulgating its statutes, or if it were so corrupt as to say that laws do not need to be promulgated, any decent man would immediately conclude, with no need to reference another standing civil code, that one must know one’s obligations in order to fulfill them. Such a requirement is in the very nature of the thing in question. As the response of the Roman citizens to Caligula’s deception reveals, there is a source of moral and legal obligation prior to the legal code of a given political community that demands that laws be sufficiently promulgated.

Caligula’s deception is a particularly vivid example, but it is by no means unique in allowing us to glimpse the existence of some natural source of normativity upon which the law of a nation must be built. Almost any significant piece of legislation can invite us to raise simple yet profound questions that point in the direction of something like a natural law that must undergird any legitimate positive law. Among those questions are the following: What is law? Is the natural source of morality truly legal, that is, a natural law properly speaking? If so, what does it mean to speak of a natural source of order in human affairs? How might we define this natural law? Whence does it come? How is it known, and how is it connected to the positive law of a given political society? Does it have some relation to the moral and intellectual virtues? In a theological register, how does the natural law stand in relation to the gift of grace offered to us by the life, death, and resurrection of Jesus Christ and the sacraments of His Church?  

I. Saint Thomas Aquinas on Law

Thomas Aquinas’s so-called “Treatise on Law” is, by any measure, one of the most influential discussions of law generally, and of natural law specifically, in the Western intellectual tradition. In what follows, we will mine his work so as to provide answers to the questions raised above. In order to articulate the nature of law and to see how natural law is distinct from but related to other species of law, we will begin by sketching Aquinas’s presentation of law in general before showing how it applies to the law of nature. Additionally, in the third section, we will complement Aquinas’s theory by drawing upon insights from Robert Sokolowski’s realist phenomenology.

A.) The Nominal Definition of Law

St. Thomas begins his discussion of law in the Summa theologiae by showing that law is an extrinsic principle of action. More precisely, he says that God is an extrinsic principle of human action and that God instructs human beings by His law.{2} A positive law crafted by human agents for a particular polity is also an extrinsic principle of human action, a source of human conduct originating outside of the person or institution moved by the law. However, law is an extrinsic principle that must be appropriated internally by those subject to it. Such legal extrinsic principles are distinct both from intrinsic principles (sources of human action abiding within the agent, such as the powers or abilities of the human soul and the virtues that perfect these powers in view of their proper objects) and from extrinsic principles that are not rationally appropriated (such as physical force or violence). Also, near the outset of his treatment of law, Aquinas gives us its nominal definition. He says, “Law is a certain rule and measure of acts in accord with which one is either induced to act or restrained from acting.”{3} Thus, Aquinas begins his treatment of law by showing that it is an obligatory standard for and source of human action originating outside of the person subject to it, at least qua subject.

Since law is a rule and measure for human actions, Aquinas further specifies that law belongs properly to reason (ratio) because reason is the rule and measure of human actions. Aquinas concludes that law can exist in two ways. “In one way, as in the measurer and ruler. And since this is proper to reason, law in this sense is in reason alone. In another way, as in the ruled and measured. And this is how law exists in all the things that are inclined in any way by any kind of law.”{4} Aquinas’s insistence that law is a work of reason that can be “in” two subjects, one as ruling and measuring and the other as ruled and measured, is a crucial component of law; it is one and the same law that is shared between the mind of the ruler and the minds of his subjects.

In connection with law’s function of being a rule and measure for human actions, its first per se property, Aquinas maintains that law has “coercive force.” This is the second per se property of law identified in its nominal definition. Law is a binding and obligatory rule for human action. He says that law gets its name (lex) from the idea of physical restraint (ligare) precisely because law obligates one to act (obligare).{5} Aquinas says, “Law by its nature has two characteristics: first, it is a rule of human acts; second, it has coercive force.”{6} These two aspects are part of the essential aspects of law, but they are not yet the essence itself of law. They are essential characteristics of law, analogous to man’s risibility and capacity to speak, and by beginning with them Aquinas leads us into the essence itself, or nature, of law.

B.) The “Scientific” Definition of Law

In the fourth article of ST I–II, q. 90, Aquinas provides the real or “scientific” definition of law. He defines law as an “ordinance of reason toward the common good from him who has care of the community and promulgated (Rationis ordinatio ad bonum commune, ab eo qui curam communitatis habet, promulgata).”{7} Since the properties of any entity flow from the essence itself, we can say that the legal properties of being a rule and measure for human acts employing coercive power “flow” from law’s being an ordinance of reason given by the political leader of a community to its citizens for the sake of securing the common good of the polity. The spatial dimensions of the prepositions ad and ab in the full definition are also important to note; they indicate that law is a dynamic, transitive action, going from (ab) the one who is in charge of the community toward (ad) the common good by way of being given (promulgata) to those who are subject to the law through rational direction.{8} Law connotes a kind of publicly manifested act of reason that moves from the ruler to the subjects in their shared pursuit of a common good.

 Although to teach is not to rule, and to rule is not to teach, the two activities exhibit an analogous metaphysical structure. The transitive nature of the act of legislating recalls Aristotle’s understanding of teaching. For Aristotle, the act of the teacher, the agent of education, is “in” the student, the patient.{9} There is only one act involved in the teaching-learning pair: it is a hendiadys, a one through two, with the two aspects “teaching” and “learning” being two profiles of the one act between the teacher and student. Similarly, although law is an extrinsic principle of human action, the act of reason of the legislator is “in” the subjects guided by his legislation. The metaphysics of transitive action clarifies the way in which law can be “in” two subjects, one as ruling and measuring, the other as ruled and measured. These are two faces of the one act of legislating.

Further, just as the act of teaching is “in” the student by disclosing some reality to him for his understanding, so too the act of legislating is “in” the citizen by making some thing, action, ability, or exemption manifest as legally available to or binding for him. Law is essentially tied to justice, whose proper object is the just thing (ius) owed from one person to another, even if the “thing” owed is some immunity or noninterference. As Aquinas says, “Law is not, properly speaking, the right itself, but is instead a sort of conception of the right (ratio iuris)” insofar as this legalized right is made known to the citizen. The direct object of the teacher is the truth to be communicated to the student, the indirect object or dative to whom the reality is manifest and thus in whom the act of teaching resides. Analogously, the direct object of the legislator is the right thing (ius) that is enrolled in the legal statute so as to be made binding for the citizen, the indirect object or dative to whom the ius is manifest as legally binding and thus in whom the act of legislating terminates.

In all transitive activities, the party perfected by the action is the recipient of the action, the patient. The telos of any transitive action is the improvement or perfection of the one receiving the act, that is, the one in which the act acts.{10} Thus, the right-thinking subject of law rejoices in the reception of a legal code. For example, the patient in a medical procedure is the one properly perfected, or improved, by the transitive actions of the doctor, and therefore the patient desires the procedure and rejoices in its completion even if it causes some discomfort initially. The doctor achieves the perfection of his art by his healing actions, but such improvement is secondary to the act of medicine as such. Because legislating is a transitive action, the subject perfected by the action is the one who is guided by the law to the common good the law makes possible. Law is therefore an act of perfecting the subjects of the law and the common good of their shared activities, which are protected and directed by the act of legislating. For Aquinas, this fact suggests a connection between the “treatise on law” and the first five questions in the Prima secundae of the Summa theologiae, where he discusses happiness as the final end of the human person. Law directs the human agent to his proper perfection and guides his search for happiness. Aquinas says:

Since (a) every part is ordered toward its whole in the way that what is incomplete (<em>imperfectum</em>) is ordered toward what is complete (<em>perfectum</em>), and since (b) a man is part of a complete community, law must properly be concerned with the ordering that leads to communal happiness (<em>ad felicitatem communem</em>). Hence, in the definition of legal affairs alluded to above, the Philosopher makes mention of both happiness and political communion. For in <em>Ethics</em> 5 he says, “The laws (<em>legalia</em>) we call ‘just’ are those that effect and conserve happiness and its elements within the political community.” For as Politics 1 puts it, a city is a complete community.{11}

Aquinas’s claim that law is directed to the communal happiness of those subject to the law echoes a classical position on law and the common good. The metaphysics of law as a transitive action connect to and clarify Plato’s claim that the leader of any group, insofar as he is true to his craft as leader, benefits not himself but those subject to his direction; the true craftsman benefits not himself but those he is responsible for directing.{12} Thus, law is the public perfecting of the rational agents subject to the law though the manifested acts of reason of the legislator in view of a common good.

C.) The Four Causes of Law

In his scientific definition of law (an ordinance of reason toward the common good from him who has care of the community and promulgated), Aquinas employs the Aristotelian procedure of displaying the intelligibility of a thing by showing the four causes of the definiendum.{13} The very structure and order of the articles in ST, I–II, q. 90 evidences this Aristotelian pattern of investigating a phenomenon by describing its causes; the four articles deal sequentially with the four causes.

In article 1, Aquinas shows that law pertains to reason, and therefore the formal cause of law is that it be an ordinance of reason or a work of intelligence. For Aquinas, the formal cause of all legitimate law, or the essence of law, is reason as ordering toward the common good. It is significant that Aquinas says reason is of the essence of law, while force of will is not. Aquinas recognizes that the will of the person who has care of the community must be engaged in order to direct his citizens toward the good,{14} but Aquinas understands the will’s involvement as subordinate to reason. The force of will, or the power that obliges the citizens to obey, is not “part” of the essence of law, nor is punishment. Power of will and coercion are properties of law, as we have noted, but they are not of the essence itself of legitimate legal enactments. On this point, Thomas Hobbes’s concept of civil law is an interesting contrast to Aquinas’s formulation of the essence of law. For Hobbes, the civil laws are commands that manifest the will of the sovereign; law is a “Sign of the Will” imposed to determine right and wrong. For Hobbes, knowledge of the law is knowledge of the “will of the Soveraign [sic].”{15} By contrast, Aquinas is rooted in Aristotle’s political philosophy, and thus Thomas explains law as the public manifestation of the reason of the legislator as this reason directs the community toward the common good. As Aristotle says, “One who asks law to rule, therefore, seems to be asking god and intellect alone to rule, while one who asks man adds the beast. Desire is a thing of this sort; and spiritedness perverts rulers and the best men. Hence law is intellect without appetite.”{16} Thus, reason undisturbed by passion is the formal cause of law. 

In article 2, Aquinas says that law is ordered to the common good as its final cause. The telos of law is the common good of the community being ruled, and Aquinas specifies that the common good to which the law inclines is the common happiness of the political community. As the end of law, the happiness of the citizens in the enjoyment of the common good serves as the first principle in practical reasoning about legislation. This happiness is tied immediately to the friendship the law must attempt to instill, for “every law aims (tendit) at establishing friendship either of men with one another or of man with God.”{17} Clearly, the common happiness of civic friendship of a political community necessarily includes the happiness of the members of that community. Law does not sacrifice the happiness of its members on the altar of the mythical happiness of the state as a whole. Aristotle criticizes Plato’s Socrates for asserting that the happiness of the city does not include the happiness of its members, especially the guardians of the Republic:

[Socrates] even destroys the guardians’ happiness, asserting that the legislator should make the city as a whole happy. But it is impossible for it to be happy as a whole unless most people, or all or some of its parts, are happy. For happiness is not the same kind of thing as evenness: this can exist in the whole but in neither of its parts, but happiness cannot. But if the guardians are not happy, which others are?{18}

Aquinas follows Aristotle on this point. The happiness of the whole city is impossible without the happiness of its parts (i.e. its citizens).{19} Charles De Koninck captures Aquinas’s idea that the common good is inextricably tied to the individual’s good: “The common good is eminently diffusive of itself insofar as it is more communicable; it extends to the singular more than the singular good does: it is the better good of the singular.”{20} Thus, to legislate for the common good is to work for the good of the community and the individuals in it.

In article 3, Thomas shows that the one who has care of the community properly enacts the law. Therefore the governor (or governing body), as the one who has charge of moving the community toward the common good, is the efficient cause of the law insofar as he rationally orders his subjects. The legislator, be it an individual, group, or the many citizens in a direct democracy, is the “craftsman” of the law who exercises legitimate political authority as agent of legislation. Aquinas argues that it is according to nature, not merely the result of a social contract or the product of artifice, that someone (or some group) should exercise political authority and function as an efficient cause of law and governance.

In article 4, Aquinas completes the causal picture by displaying promulgation as the material cause of the law. Promulgation is the material substrate of legislating; more precisely, the words in which the law is promulgated are the potential activated by the ruling reason of the legislator. The promulgated words are the potency out of which law comes. Since law is an act of reason shared between intelligent agents, promulgation through language is the material cause of law when the form of law, the ruling and measuring reason, is in the community of minds that are now shaped by the promulgated words and able, as rational entities obliged by the law that is promulgated to them, to be activated toward the common good. It is necessary and fitting for this process to take place via speech, which Aristotle identifies as the doorway to political life. As St. Thomas says, “Law has coercive power inasmuch as it is promulgated by the ruler or prince. And it is discourse (sermo) proceeding from some prudence and intellect directing toward the good.”{21}

II. The Contexts for and Subject of Natural Law Theory

Before applying the above reflections on law in general to the natural law, it is important to note that the title “natural law” is used and developed in many different ways and for varied purposes, so it is helpful to clarify the context within which we will study the natural law. Additionally, the very object of natural law, the target that we wish to shed light upon when we engage in natural law thinking, is inherently complex. Therefore, we will also discuss the precise subject articulated by theories of natural law.

A.) Three Contexts for Natural Law Thinking

Russell Hittinger distinguishes three “contexts” in which the natural law is employed: (1) the systematic, (2) the dialectical, and (3) the dialogical.{22} Hittinger says that natural law thinking within the systematic context “is not immediately concerned with making moral arguments, but rather with making coherent the sources of truth, including what is recognized or presupposed about the natural habitat of reason.”{23} The systematic context is the most comprehensive and contemplative of the three; natural law thinking within this context is concerned with identifying and integrating the sources of knowledge of the natural law. Within the dialectical context, philosophers begin with a concrete, disputed moral question, which is usually occasioned by current cases or moral dilemmas, and attempt to reason to a specific conclusion. Thus, natural law thinking within the dialectical context seeks to answer a pressing moral question by applying the natural law to a concrete case. Finally, interlocutors operating in the dialogical context do not search primarily for answers to specific moral questions or for the coherence of the sources of truth; rather, they use the natural law as an aspect of the search for common premises across religious and philosophical traditions. Hittinger says that natural law thinking in the dialogical context is “a search for common and converging pathways of evidence.”{24} All three contexts are intertwined, so a development in one area has consequences for the other two. However, each of these three contexts for reflection on the natural law has its own integrity and proper method of investigation.   

In this essay, we are operating within the “systematic” context of natural law thinking. Although we will use concrete examples to illustrate the points being discussed, the end in view is not to resolve a complex moral question. Nor are we explicitly concerned with the search for common and converging pathways of evidence with various philosophical or religious traditions. Our aim is more speculative; it is simply to understand the nature, as it were, of natural law.{25}

B.) Natural Law and the Three Foci of Order

Let us now further specify what we mean by the title “natural law.” Yves Simon says that there is an “eternal return” of natural law thinking despite the vast changes that have taken place between pre-modern and modern philosophies, social institutions, and political forms.{26} Part of the reason for this “eternal return” of the natural law is the fact that a natural law theory, as Simon says, seeks to discover the “prior premises” of human positive law.{27} The natural law premises are “prior” in a primarily ontological sense; the “prior” is not just chronological in the sense that we have these issues even before explicitly engaging in politics, but also permanent and ontological in that they are the constant source of positive law and also the basis for our ethical interaction. Thus, natural law theory seeks to answer ultimate questions about the source of authority and justice. According to Aquinas, and as we have seen from Caligula’s legal adventure, prior to the order in human affairs introduced by the positive law, human life and the natural world already exhibit an ordered structure. Therefore, an investigation into natural law as the “prior premises” for positive law and for moral interaction involves the distinction between “three foci of order” that are more fundamental than the positive law.

Following Simon’s thought, Hittinger says that the prior premises of natural law coalesce around the three foci of “order in nature, order in the human mind, and order in the divine mind.”{28} In response to the question “What is a theory of natural law a theory of?” Hittinger says:

In the first place, natural law can be regarded as an issue of propositions that are first in the order of practical cognition. On this view, a philosophical account of natural law endeavors to bring into focus those “reasons for action” antecedent to reasons yielded through practical deliberation and judgment. In the second place, natural law can also be regarded as an issue of nature or human nature, in which case natural law is not only a problem of the logic and epistemology of practical reason, but also a problem of how practical reason is situated in a broader order of causality. Finally, natural law can be approached not only as order in the mind or in nature, but as the ordinance of a divine lawgiver.{29}

These three foci provide a foundation for the institution of positive law in a political community. We identify (1) order “in” the human mind in the form of propositions that provide direction for moral action prior to our individual deliberations and decisions about what must be done in a concrete situation. These general propositions, such as the prohibitions against murder or adultery, provide a basis for moral deliberation and judgment. However, order in the human mind can be seen in relation to (2) a broader order of causality within the natural world. That is, order in the human mind is somehow shaped by our interactions with the natural entities that we, in company with others, confront in experience. Such experience enables us to actualize our own nature with its finalities and native excellences, which, as we will show in subsequent sections, are normative for our intentions and actions. Finally, these first two foci of order are both seen as expressions of (3) order “in” the divine mind. Natural law thinking, especially within the “systematic” context, involves distinguishing these three foci of order and contemplating how they are integrated with each other.

C.) Natural Law as Law to the Highest Degree

Are these threefold foci of order that provide a natural source of normativity truly legal, or are they merely an important prelegal guide to positive law and morality? Is all law positive law? Two texts from St. Thomas are crucial for answering the question of natural law’s legality, and taken together they appeal, at least implicitly, to the interconnection between order in the divine mind, in the human mind, and in nature. In the first text, Aquinas presents the following objection to his claim that promulgation belongs to the essence of all authentic law. The objector says, “Natural law has the nature of law to the highest degree (maxime habet rationem legis). But natural law does not require promulgation. Therefore, it is not part of the nature of law that it be promulgated.” Although the statement “natural law has the nature of law to the highest degree” comes from the objection, Aquinas accepts this position in his reply. He says, “The promulgation of the law of nature consists in God’s having instilled it in the minds of men in order that they might know it naturally.” Thus, Thomas confirms the objector’s idea that natural law is most properly called a law, and he suggests the mode in which the natural law is promulgated by its Divine author, moving “from” the order in God’s mind “to” the order “in” the human mind. In the second text, Aquinas says, “But it is evident that human acts can be regulated by the rule of human reason, which is gleaned (sumitur) from the created things that man knows naturally.” The rule of human reason, or what we may call the natural law, comes to us from God “through” the order in the nature of things, an order that the human mind grasps and imitates in its own actions. Stephen Brock argues that the natural law is promulgated to us through the “instrumentality of nature” and through the activities of human reason as it is taught by the Divine artist’s work in the natural world.{30}

Aquinas therefore argues that the natural law is truly legal. It has the ratio of law to the highest degree, and the integration of the three foci of order enables us to see its legality. In the following sections, we will flesh out each of these three sources of order, and their relationship to each other, so that we will be able to give both a nominal and real definition of natural law.

III. Toward a Nominal Definition: Order in Nature and in the Human Mind

A.) Order in Nature

Hittinger is certainly correct when he says that Aquinas’s natural law theory depends upon a “philosophical explication of the interrelation between inclinations, goods, and precepts, which in turn presupposes the intricate groundwork laid in philosophy of nature.”{31} Thus, in order to specify the order in nature and show its connection to order in the human mind and order in the divine mind, we must lay down some of the “intricate groundwork” of an Aristotelian philosophy of nature, which is as perennial as it is timely. Aristotle claims that certain things exist by nature and that each natural thing has “in itself a source of motion and rest, either in place, or by growth and diminution, or by alteration.”{32} As distinct from artificial things, natural beings have, indeed in some sense are, their own intrinsic sources of unity and their own innate inclinations to change, “since nature is a certain source and cause of being moved and of coming to rest in that to which it belongs primarily, in virtue of itself and not incidentally.”{33} It is of course the form that is “more the nature” of the thing than its matter, for the form is the activity by which its material-potency is unified as the kind of thing it is and thus shaped toward its proper actions.

Further, Aristotle says that it is absurd to attempt to prove that natural things exist, not because such a proof would be too difficult, but rather because the existence of natural entities is too manifest to be subject to proof. “That nature is, it would be ridiculous to try to show, for it is clear that among the things that are, such things are many. But to show things that are clear by means of things that are unclear is the act of one who cannot distinguish what is known through itself from what is known not through itself.”{34} In his commentary on this text, St. Thomas says that the existence of nature is known through itself (per se notum) because the very being (esse) of natural things is manifest to the senses, but what the nature of each thing is, or what its principle of motion might be, is not as immediately manifest.{35}

Although what the nature of each thing is cannot be as immediately known as that nature exists, we would be mistaken to conclude, in quasi-Kantian fashion, that the natures of things are therefore shrouded in secrecy. What each thing is, i.e., its nature, is manifest by its actions. As Aquinas says, “We know the substance of a thing from its properties or operations,” for “the nature of an entity is displayed by its operation.”{36} In the order of being, the essence or nature of each thing “flows” into its powers or native abilities, which are in turn activated by the thing’s operations, its activities. Therefore, in the order of discovery, “The operation of a thing manifests both its substance and its existence, since a thing operates according as it is a being, and its proper operation follows upon its proper nature.”{37} The nature of each thing is disclosed by its actions, which actuate the powers that flow from its essence. As the poet tells us, “As kingfishers catch fire, dragonflies draw flame.” Because “the operation of a thing shows forth its power, which points to (indicat) its essence,” the intellectual priority of knowing that nature exists “before” knowing what the thing is in its nature is primarily logical, not temporal or ontological.{38} 

While all the accidental features and activities of a thing reveal something of its being and nature, it is the active ergon of the entity, its characteristic and distinguishing operation flowing from its form and activating its specific potentials for action fitting for it according to its kind, that primarily achieves the display that is the entity’s intelligibility to us. Such activities are first for us in our encounter with things, and Aristotle claims that the human being is no exception to this natural rule. The human being himself, qua human being, has an ergon flowing from his nature. “Are there, then, certain works and actions of a carpenter and shoemaker, but none of a human being: would he, by contrast, be naturally ‘without a work’? Or just as there appears to be a certain work of the eye, hand, and foot, and in fact of each of the parts in general, so also might one posit a certain work of a human being?” Aristotle identifies this natural work of the human being as “activity of the soul according to reason (kata logon), or not without reason.” Human nature expresses itself “as a certain life, and this is an activity of the soul and actions accompanied by reason (energeian kai praxeis meta logou).”{39} Our natural function is to live in accord with logos, to think and to act according to reason and its disclosure of reality, and therefore Aristotle’s preferred “definition” of human beings, his articulation of human nature, is that we are the animals possessed of logos.{40}

This ontological structure of nature expressing itself in its characteristic work, its ergon, is the basis for understanding the good of each thing, since its goodness is nothing other than the perfection of its characteristic operations flowing from its form. Because the ergon of a thing, its characteristic job or function, is rooted in the nature of the thing, and because the perfection of its ergon is the well-being or flourishing of the thing itself, each entity is good, and therefore intelligible, inasmuch as it is perfect, insofar as it achieves its fullness of being through the activity of the virtues proper to it; for its virtues are but the perfections of its ergon, making the thing good by enabling its function to reach its natural end smoothly and consistently. The sharpness and sturdiness of the knife perfect its function of cutting, thus making it a good knife and allowing it to show forth as a paradigm of the “nature” of knives; art and human reason, after all, imitate nature. The healthy, vig­orous, and therefore good dog is more intelligible as a dog than is the sickly, moribund one because his “doggy” function has been perfected by the relevant virtues. The active and perfected ergon of a thing is its brilliant goodness, its beauty, and therefore its radiant intelligibility shining brightly for us. Brilliance is goodness achieved and thus nature manifest, or nature manifesting itself in its excellence. As Aristotle says, “Nature is an end and a that-for-the-sake-of-which.”{41} In the realm of human action, because we are by nature the animals having logos, our natural “job” is to develop the virtues that enable us to live in accordance with logos and its natural end of truth. The man who does so invites our admiration because he shows us what we are by nature; he reveals us to ourselves.

Étienne Gilson argues that this teleological and disclosive understanding of nature has not been discredited by the advent of evolutionary theory or the advances of modern science more generally.{42} Further, he recognizes this sense of nature as that which primarily distinguishes Catholic intellectuals from the excesses of modern scientific culture and, we might add, from the increasingly fantastic flights of anti-natural, self-creative fancy characteristic of modern and postmodern thought.{43} It is also the necessary and good foundation of Thomas Aquinas’s natural law theory, for we cannot understand what the natural law is without this grasp of the natures of things as they stretch themselves out toward their own perfections, which in turn manifest the natures they complete.

B.) Order in the Human Mind

We have seen that human nature is ordered to its own natural ergon, toward the activities of reason and to a practical life in accordance with reason. St. Thomas also argues that reason itself exhibits a natural order of “being-true-good” in our encounter with, cognition of, and desire for things. He says, “The intellect apprehends primarily being itself (ipsum ens); second, it apprehends that it understands being (ens); and third, it apprehends that it desires being (ens). Hence, first is the idea of being (ratio entis), second the idea of truth (ratio veri), and third the idea of good (ratio boni), though good is in things.”{44} As rational agents, we must have some basic insight or understanding of what something is and how it is fitting for us if we are to desire it as good, for “cognition naturally precedes desire.”{45} The mind’s order of being-true-good is not achieved in a mental cabinet separated from the existence of things; rather, it is the way the mind encounters things, for truth is “closer” — more immediately related to the being of the thing known— while the good of a thing is its perfection or well-being. The intellectual and volitional order being-true-good tracks the ontological order in the nature of things. This metaphysical principle of the priority of the truth of being to the good is at work throughout Aquinas’s thinking on natural law.

As we encounter the being of things and “move” from being to truth to good, we begin to disclose a natural rule and measure of human actions, and the activity of synderesis plays an important role in this discovery of natural law. Medieval discussions of synderesis, including Aquinas’s, take their departure from a text in St. Jerome’s early fifth century commentary on the Old Testament book of Ezekiel.{46} Among the issues raised by St. Jerome and discussed by medieval thinkers are the following: (1) Is synderesis a power (or faculty) of the human soul or a habitus? (2) Is synderesis cognitive or affective? According to Aquinas, synderesis is a natural habit or ability of human practical rationality that enables us to recognize (cognitively) the first principles of the moral life, and it is therefore the source of our natural knowledge of the precepts of the natural law.{47} Aquinas says, “The act of the natural habit called synderesis is to warn against evil and to incline to good.”{48} The natural, rational “habit” of synderesis is not developed by us through repeated actions; it is given to us by God in our rational nature, and it is part of the order “in” the mind that enables us to live by the natural law.

Let us move from synderesis as the habit “containing” the precepts of the natural law to the precepts themselves. In an important and oft-disputed text, Aquinas specifies that the primary precepts of the natural law are per se nota, just as the primary principles of speculative reason are per se nota. A per se notum proposition is “known in itself.” It requires no proof because the predicate belongs “immediately” to the subject; the necessary connection between the subject and predicate does not depend upon a middle term functioning in a syllogism.{49} Aquinas distinguishes two ways in which a proposition can be per se notum: (1) in its own right (secundum se) and (2) in relation to us (quoad nos). A proposition is per se notum in its own right if the predicate is in fact included in the notion (ratio) of the subject, but a proposition that is per se notum in itself may not be immediately known as such to a person who does not understand that the predicate in the proposition belongs to the very ratio of the subject. For example, that law must be directed to the common good of communal happiness is per se notum secundum se, but it may not be per se notum in relation to someone who has lived his entire life under the rule of a tyrant. For this reason, many propositions that are per se nota in themselves are known as per se only by the “wise” (sapientibus), who understand the meaning of the words in the proposition.{50}

However, Aquinas says there are certain fundamental truths and propositions that are per se nota both in themselves and to everyone (dignitates vel propositiones per se notae communiter omnibus). He says that these propositions “are the ones whose terms are known to everyone, e.g. ‘Every whole is greater than its part’ and ‘Things equal to one and the same thing are equal to each other.’”{51} Aquinas then presents a tightly ordered structure of the derivation of natural law precepts.

Aquinas argues that being (ens) is “the first to fall” within human apprehension; therefore the ratio of being and nonbeing is the foundation for the first indemonstrable principle (the principle of noncontradiction), which is that the same cannot be affirmed and denied (at the same time and in the same way).  Aquinas’s discussion of the precepts of natural law therefore begins by focusing on the way being is and how our intellectual activity is formed by the way things are manifest to us.  

Next, although Aquinas does not mention the role of truth explicitly in this article, it is clear that he sees the role of the intellectual achievement of truth as in some way coming “between” our grasp of being and our pursuit of the good. As we have seen, Aquinas says that there is a natural order of “being-true-good” in our interactions with the world.{52} As rational agents, we must have some basic insight or understanding of what something is and how it is fitting for us if we are to desire it as good.{53}

Aquinas then argues that while being is the first to fall within apprehension simply speaking, good (bonum) is the first to fall within the apprehension of practical reason: “Every agent acts for the sake of an end, which has the character of good (boni). And so the first principle in practical reasoning is what is founded on the notion of the good: The good is what all things desire (quod fundatur supra rationem boni, quae est, bonum est quod omnia appetun). Therefore, the first precept of law is that good is to be done and pursued and evil is to be avoided. And all the other precepts of the law of nature are founded upon this principle.”{54} Just as with the principle of non-contradiction, the primary precept of the natural law is based on the ways things are; the good is “in” things, and it is the goodness of things, such as life, family life, virtuous friendships, communities of people searching for the truth about God, that should be intelligently incorporated into our lives. The primary precept of the natural law spoken to and by us through synderesis is to do good and avoid evil, and it is per se notum both in itself and to us.{55}

Aquinas then goes on to show that the other precepts of the natural law flow from this first practical precept that good ought to be done and evil avoided. He says that whatever (omnia) human agents naturally grasp as good (or its contrary evil) pertains to the natural law as to be done (or avoided). The good, as we have seen, is the perfection of an entity, its fullness of being achieved upon the completion of the virtues that perfect its natural functions. And precisely as perfect, a good thing is desirable. A human good is that which is desired as having some perfection in itself and, as such, as being perfective of the human person. It is desired because it is good; it is not good because it is desired. As Aquinas says, “Good exists in a thing so far as that thing is related to the appetite—hence the aspect of goodness passes from the desirable thing into the appetite, insofar as the appetite is called good if its object is good.”{56} We naturally desire our own fullness of being and perfection, i.e., our happiness, which we obtain through properly orienting ourselves to other people and to goods outside ourselves. We see certain things as goods, as perfect as the kinds of things that they are, and precisely as such we desire them as partaking in or contributing to our own goodness, our own fullness of being, and our own perfection. I see the beautiful bourbon as having a fullness of being, as exhibiting the excellences that make it to be not only bourbon, but good bourbon, and precisely as such I desire it as something that perfects me in due measure, as having the particular aesthetic appreciation of a well-crafted spirit.

Since the good has the ratio, i.e., the idea of an end to be pursued, the rational grasp of a good naturally fitting for human beings gives rise to a natural inclination to that good. In turn, the order of the natural law precepts mirrors the order of natural inclinations, for “there is an ordering of the precepts of the natural law that corresponds to the ordering of the natural inclinations.”{57} Aquinas distinguishes three kinds or levels of natural inclinations to natural goods that perfect human beings: to the good of conserving one’s being according to one’s nature, which man shares in his own way with all substances; to the good that nature has taught all animals, namely the union of man and woman and the rearing of children; to the good of knowing the truth about God, as well as to the good of living in society, all of which are unique to man as the animal with logos.

St. Thomas therefore argues that human persons have a natural—and I argue rational—inclination to the good as known naturally by reason. He shows that this natural perception of the good is specified, or filled in, by recognizing the goods (1) of conserving one’s being according to one’s nature; (2) of marriage and familial society; (3.a) of knowing the truth about God, and (3.b) of living together with others in political society.{58} Because human persons naturally recognize these personal, social, and theological realities as goods, they have natural inclinations (1.i) to conserving themselves in being in a way fitting for human nature; (2.i) to marriage and familial society; (3.a.i) to knowing the truth about God; and (3.b.i) to life in political society. As rational inclinations, these are inclinations of the will, the spiritual and rational appetite whose proper object is the good understood by the intellect.{59} The precepts of the natural law are distinct from these inclinations but flow from them, so these precepts protect and promote those goods the knowledge of which gives birth to the natural inclinations. The natural law precepts demand that one avoid offending those with whom one lives; that one avoid ignorance (especially about God’s existence and nature), that one avoid fornication, adultery, and those activities destructive of marital life and the education of children; and that one take reasonable care for the continuance of one’s own life.{60}

It is important to stress that these goods are aspects, or ingredients, of human happiness. One cannot be happy or flourish as a rational animal unless one conserves one’s being according to one’s nature, for well-being demands being. One cannot be happy outside of properly ordered familial and political societies, to say nothing of the myriad intermediate societies through which we develop moral and intellectual virtues, such as schools and voluntary associations of various kinds. One cannot be happy unless one searches for and rejoices in the truth about God, Who is the highest and first truth.{61} The natural law is therefore an authoritative directive toward human happiness in the myriad friendships that perfect our nature as rational and thus social animals. Friendship, after all, is the end (finis) of law.

St. Thomas’s presentation of reason’s disclosure of the truth of being as foundational for our natural pursuit of the good can be strengthened by appealing to Robert Sokolowski’s phenomenological discussion of veracity. Sokolowski says that veracity names “the human inclination to attain the truth of things.” He argues that such veracity should not be taken as a virtue. It is not the result of our successful cultivation of certain natural abilities. Rather, veracity “is something more elementary [than a virtue]. It is with us from the beginning. Veracity is the impulse toward truth, and the virtue of truthfulness is its proper cultivation. Veracity is the origin of both truthfulness and the various ways of failing to be truthful.” Sokolowski says that veracity “means practically the same thing as rationality, but it brings out the aspect of desire that is present in rationality.” More specifically, “veracity is the desire for truth; it specifies us as human beings. It is not a passion or an emotion, but the inclination to be truthful.” Veracity is the “eros involved with rationality,” and we may add that it therefore highlights the rationality of the will, the rational appetite whose inclinations are so central to the natural law. Veracity is the open-ended, undifferentiated tendency toward truth as such; it is not limited to a particular kind of truth, and it is also not the result of a choice on our part. Veracity is more fundamental than choice itself, and it is part of what makes human choice possible, since it shows that we are geared by nature toward discovering the truth of things.

Sokolowski’s presentation of veracity should be linked with Aquinas’s primary precept of the natural law, which is “good is to be done and pursued and evil avoided.” We cannot be taught to pursue good and to avoid evil, nor can this primary precept be forgotten or “erased from our hearts,” just as we cannot be taught to desire truth, and we pursue the good as an aspect of our desire for the truth. Veracity, our natural “inclination to be truthful,” sets the stage for our natural inclinations to the goods perfective of our nature as rational animals, animals having logos. Even our willing is a feature of our veracity, for “it is manifest that reason in some sense precedes the will, and orders its act, insofar as the will tends toward its object according to the order of reason, given that the apprehensive power presents the appetitive power with its object.”{62} As soon as we begin to act as responsible agents, we naturally and inevitably tend toward the true and the good in our thinking, speech, and actions. We do well therefore to highlight our natural veracity as the lens through which the being of the good shows itself to us. The good is that which all desire, and it shows up to us human beings precisely in our rationally desiring it, i.e., in our intelligent and truthful pursuit of it. As inclinations of the will, which stem from reason’s grasp of the truth about the good, the natural inclinations to being, to marriage and family life, to the truth about God, and to life in society are expressions of our veracity, that is, our rational will to live the truth in love.      

C.) The Nominal Definition of Natural Law

Earlier, we quoted Aquinas’s claim that “it is evident that human acts can be regulated by the rule of human reason, which is gleaned (sumitur) from the created things that man knows naturally.” The created things in nature exhibit an order that is formative for the order in the human mind, and this correlation between nature and the human mind provides a foundation for the nominal definition of natural law. Aquinas argues that reason imitates nature because reason unifies things by ordering imperfect parts to more perfect wholes. Reason, taught by nature, moves teleologically from simple, imperfect parts toward complex, perfect wholes in which some activity or mode of life finds its completion or perfection. A craftsman makes a ship from many simpler, less perfect parts, and human beings themselves are “parts” of larger social wholes in which they naturally desire to live.  

Reason’s imitation of nature includes an imperative to respect the order that it finds in the nature of things, especially human nature. Francis Slade and Sokolowski therefore argue that the natural law can be understood as “the ontological priority of ends over purposes.”{63} The end of an entity, understood as the goodness of the entity, its being most fully what it is by reaching the perfection of its nature, is ontologically prior to our purposes, or intentions, in acting because these purposes can and do fluctuate. The end of a thing is more ontologically solid, more stable and permanent, and hence more “rooted in being” than the purposes of a human agent. As Slade says, by recognizing the ontological priority of ends over purposes, we are arguing that “actuality stands higher than possibility.”{64} We can distinguish two ways in which the ends of things exhibit an ontological priority. First, the eidos-telos of an entity “governs” the substrate activated and unified by the eidos. It is the form of an entity that shapes the matter towards the perfection (end or telos) of the entity as a unified whole. Second, the ends of things measure the purposes of the agent who must actualize these ends. The second kind of priority is parasitic on the first; ends measure human purposes because they govern the structure and activities of things.

Although this definition of natural law speaks of the ontological priority of ends over purposes, it also manifests what is first in the order of discovery; it is the first way that the natural law is disclosed “for us.” Lawrence Dewan makes a similar point: “Reason puts nature first . . . because reason sees ontological priority. Goodness is seen in ontological order, and reason’s giving nature priority is the recognition of that order. The ontologically determinate (i.e., nature) has more of the aspect of being than has the ontologically determinable (the operable or choosable).”{65} The “ontologically determinate” order in nature (the ends of things) functions as a measure for the ontologically determinable order in the human mind (art and human action). Therefore, the “ontological priority of ends over purposes” can be considered the nominal definition specific to the natural law; it is the initial way that we constitute a natural rule and measure for our actions.

In order to see the natural law as the ontological priority of ends over purposes, we must learn to distinguish between three things: (1) the ends of entities that we use and encounter (including the ends of human nature); (2) the purposes we have in making our decisions; and (3) the laws and customs of our community. When we make these distinctions, we see that we are measured, not by our own purposes, nor even, ultimately, by the laws and customs of our community, but first and foremost by the ends of things, in particular the ends of human nature we have identified (life, marriage and family, truth, God, and society).  

As we have seen, ends are “in” things; the end of a thing is its native excellence, i.e., its good. As Slade says,

“End” as a translation of telos means what a thing will be that has become fully determined in its being; the defined; the complete; a condition of perfection, completion, fulfillment. “End” as a translation of telos does not mean “termination,” as when a road ends in a “dead end”; it does not signify that something no longer exists, as when we say that “death is the end of life.” End, as telos, signifies a continuing state of perfectedness; it is akin to the meaning of “finish,” where we are speaking about what the cabinet maker does last in making a piece of furniture: he puts the finish on it, i.e., brings it to perfection in completion.{66}

While ends are “in” things independently of our decisions concerning them, our purposes or intentions are up to us, as Aristotle says. Driven by the desire for happiness that animates our moral thinking and decision making, we begin to make decisions based upon rational desires, or what Aristotle calls “wishes” (boulēseis). Aristotle says that we can wish for impossible things, or we can wish for things that are possible but not by our own agency; and finally we can wish for things that we can bring about by ourselves or with our friends.{67} When this last form of wishing begins to direct our moral deliberations and conduct, such wishes become purposes. Sokolowski says, “Purposes or intentions are wishes that have kicked into action.”{68} Purposes are what we set down for ourselves; purposes are our intentions in acting, and they only come about with our thinking and willing. “Purposes, therefore, can exist only in human beings . . . .  There are purposes only in the strict sense when there are men.”{69} We are the rulers of our purposes and thus free to devise them as we direct our actions.

Although we are free to form and direct our purposes, we cannot change the ends of things:

End, as telos, is not synonymous with “purpose,” although the words are commonly understood to be, and are used as, synonyms. But telos does not mean purpose. Agents and actors have “purposes” by which they determine themselves to certain actions. Purposes are motives, “motors” propelling us toward destinations. Ends (telos), on the   other hand, are characteristic of all kinds of things; the end of the axe is “cutting,” but the axe executes no purpose in its cutting. Those who use axes, the agents, have many purposes: to clear land, to obtain firewood, to blaze trails, to attack someone, etc. Ends are not executed by agents. Purposes require agents. Purposes belong to agents as they determine themselves to actions.{70}

While ends and purposes (or agents with purposes) are always interacting in our moral transactions, ends simply are what they are quite apart from our desires. While both ends and purposes are good “things,” they are good things of different ontological orders. 

Aquinas argues in a similar way. He distinguishes between the finis operis (end of the work) and the finis operantis (end of the worker). The finis operis for Aquinas is comparable to what we have named ends, in this case the ends of activities, while the finis operantis is akin to what we have named purposes. Aquinas says, “It must be observed that sometimes the end of the worker (finis operantis) differs from the end of the work (finis operis), thus it is clear that the end of building is a house, whereas sometimes the end of the builder is profit.”{71} Aquinas also says that the “right ends (fines recti)” of human life are “fixed (determinati),” but the means to achieve these ends exhibit great variability.{72} This distinction between the fixed ends of human life and the variable means to achieve those ends fits well with the distinction between ends and purposes. Further, Aquinas argues that the ends of things (and activities) are normative for our actions. He says, “It is good for each person to attain his end, whereas it is bad for him to swerve away from his proper end. Now, this should be considered applicable to the parts, just as it is to the whole being; for instance, each and every part of man, and every one of his acts, should attain the required end.”{73} Also, he says, “Every human act that is not proportioned to the proper end is said to be disordered.”{74} Given the natural inclination to the end of life, given what the ends of the body are, and given what food is, eating will be disordered if it is not in line with or works against the health of the human body. While our purposes in eating could be varied, we simply cannot make it the case that the end of the body is sickness and that food should serve to make us ill.{75} We can only align our purposes in eating with the end of health. The same line of reasoning can be seen in any area of human activity. A man may intend to use language to lie or mislead others so as to attain his desires, but he simply cannot make the end, or perfection, of speech itself to be deception.{76} Another man may have the purpose of cheating a business partner by manipulating a contract, but he cannot make the end of contracts themselves to be manipulation. These examples manifest what it means to say that the natural law is the “ontological priority of ends over purposes.” Our freedom in setting our purposes carries a responsibility to align our intentions with the ends of things, especially the ends, the goods, of our rational inclinations. 

We can successfully pursue our natural ends as human agents, the ends of truth and happiness in familial, religious, and political life, only by coming to know ourselves in our grasp of the eidos and telos of things through language. Language is the doorway to social and political life, and it is also our entrance into the intelligibility of things that reveals their ends, or perfections, which are in turn normative for our intentions. It is by interacting with things rationally that we bring ourselves to light as rational agents with our own natural ends and perfections. Once we grasp what a thing is, and hence what its perfection is, we are enabled to distinguish it from our own purposes and therefore interact with it properly, thus strengthening our natural inclinations to our proper goods. Even at the level of artifacts, we see that the being and end of a thing provides us with a measure for how we are to interact with it. We should kick the soccer ball, not the dinner plate. At the level of animate life, we should pet the dog, but not the alligator. As we learn to act in associations with other human persons, we see that, given their ends as agents of truth, we must love ourselves by treating them with a certain level of respect. However, we are only able to adapt our behavior adequately to the being and ends of things if we make the distinction between ends and purposes, with the concomitant realization that ends are ontologically prior to purposes. 

We must, however, answer an objection to our view of the natural law as the ontological priority of ends over purposes. One may claim that our view of natural law has the necessary consequence of locking us into a radical, universal form of pacifism. It could be objected that our position would entail a complete abstention from killing or harming any living creature for any purpose. However, we can answer such an objection with an appeal to Jacques Maritain’s understanding of the “Republic of Natures.”

It is not simply that through language human reason beholds individual entities acting in an ordered way toward their own specific ends, as if we encountered entities in a vacuum. According to both Aristotle and Aquinas, a natural agent’s movement toward its end propels it into an integrated lattice of interacting natures. That is, the natural entity’s order to its perfection is always situated within a more expansive order of all the “parts” of the natural world to each other. Aristotle says, “And all things are ordered together somehow, but not all alike, both fishes and fowls and plants; and the world is not such that one thing has nothing to do with another, but they are connected. For all are ordered together to one end.”{77} Thus, each individual thing is inclined toward its perfection by operating within a wider web of interacting natures.

We can therefore distinguish between two kinds, or two levels, of order in nature: (1) the order of each entity toward its perfection (the order of the part to its perfection within the whole), and (2) the order of all natural things mutually influencing each other and their environment (the order of the whole itself, or the order of all the natures to each other within the whole). Maritain captured the relation of these two levels of order with the phrase “The Republic of Natures.”{78} The key is to understand that these kinds of order are not merely unopposed, but rather they are dependent upon each other and complementary; the interaction of different natures on the larger scale is organized harmoniously precisely through each individual nature operating according to its inherent dynamism for perfection. Thus, to know an entity is also to know how it interacts with other beings, both as an agent and as a patient. To know a dog is to know how it interacts with cats and with humans; to know a cow is to know that it wanders freely and grazes in a field, and to know a lion is to know that it eats other animals. Knowing an entity means seeing how it achieves its perfection through interactions with others.  

This view of the Republic of Natures holds that intellectual creatures occupy a special place in the hierarchy of natural entities. Aquinas argues that nonhuman entities are “for the sake of” human beings in the sense that we are responsible for using them intelligently:

We see that things do go on in the course of nature in such a way that intellectual substance uses all others for itself: either for the perfecting of its understanding, since it contemplates the truth in them; or for the exercise of its power and the development of its knowledge, in the fashion of an artist who develops his artistic conception in bodily matter; or even for the support of his body which is united with the intellectual soul, as we see in the case of men.{79}

Because (1) the good of the whole is better than the good of the parts and (2) the good of the whole consists in the mutual ordering of the parts, Aquinas says that the good of the universe requires that the parts be ordered to the perfection of the whole insofar as one part is made to serve another. Thus, the ordering itself demands that the lower natures be subordinate to the higher, and the human agent is higher than other animals precisely through the operations of thinking and willing, operations which enable him to know the “whole of things,” even if not wholly.{80} Aquinas therefore says, “It is not contradictory for some natures to be for the sake of the intellectual ones, and also for the sake of the perfection of the universe. For, in fact, if the things needed for the perfection of intellectual substance were lacking, the universe would not be complete.”{81} Thus, the ends of things must be seen within a natural hierarchy with the human agent occupying a unique and important place. 

The ends of things provide the ontological structure within which we can harmonize our actions and pursue common ends through common actions; ends give us a common standard of excellence in human action. The ends of life, of marriage and family life, of savoring the truth about God, and of life in political society are the goods that are naturally normative for our purposes and intentions, and those human ends are set within the context of a natural world that offers itself as a structure of interlocking teleology. What we are describing could be called a cosmos, an ordered and beautiful whole. Rémi Brague describes this understanding as follows: “The world as cosmos, as beautiful and good order, is a law. The cosmos indicates to us a sort of law that we must follow. It is therefore the rule, it should be the rule of our action.”{82} There are various reasons why an individual may not be able to distinguish the proper ends of things from his purposes (and there are various factors that may prohibit him from seeing the world as a cosmos), but the key is that the natural law will “dawn” on him as he begins to distinguish them more explicitly.

For the natural law to direct us more efficaciously, a similar distinction must be made between the ends of things and the positive laws or customs of our community (between physis and nomos). The ends of entities come into sharper focus for us when we are able to see them as distinct from both our purposes and also the customs of our culture.{83} The laws of a country may respect the ends of things or they may vitiate them, but living by the natural law entails seeing that the natural goodness of things is more fundamental than the laws of a community. This distinction often arises when positive laws are opposed to some natural end or when these laws are inadequate in some domain of human action. However, the distinction need not manifest itself in a state of conflict between the natural end and the established law of the land. The key is to distinguish what is good by nature, what fits with the ends of the thing in question, and what is good by legal decree or culture. It requires seeing what Aristotle calls the “naturally just” as the foundation for the “legally just.”{84} It is simply good to tell the truth to a jury in a legal proceeding, and the goodness of this action is confirmed but not originally established by positive laws forbidding perjury. Also, the goodness of honest speaking is distinct in kind from the goodness of driving on the right side of the road in the United States, although both are in fact good things to do. Distinguishing these dimensions of goodness is an achievement of human intelligence in which the natural law comes to light.

Once we make the distinction between what is good by nature and what is good by custom or legal decree, we can recognize that the goodness of customs and positive laws rests on what is good by nature, and in two ways. First, positive law must enshrine in its statutes those conclusions that are directly based upon natural law principles, such as the prohibition of murder and theft. Second, the positive law must specify many of the principles or conclusions of natural law by extending them into the realm of concrete, historically shifting circumstances that obtain within a given polity.{85} Natural law principles are at work in a decent tax code, but such legislation is further downstream than is the law against murder. As Hittinger says, “Human nature is a norm for what can count as rational in the domain of conduct and conventions or contracts. Conventions, it is plain to see, can also be norms, provided that they do not contradict the implicit and discoverable norm of human nature.”{86} Customs and human conventions do bind human agents, but these conventions, if they are just, “presuppose the rudiments of a natural human dignity consisting in the form, the ends, and the operations of human nature. Only thus can nature be a norm with respect to convention.”{87} To be sure, Aquinas argues that not every vice that violates the natural law should be outlawed in a given political society, but the positive law must prohibit those actions that strike at the very heart of human nature and social life, such as murder and theft.{88}

For example, given the unitive and procreative ends of human sexuality and the nature of marriage and family, contraception is a violation of the natural law, regardless of the purposes of men and women who consensually engage in sex or the customs of a given society. Yet, the question as to whether or not a specific polity ought to legalize contraception will depend in part upon the moral status of its citizens and their ability to live in accordance with such a regulation. As St. Thomas says, men and women, and indeed whole societies, can become blind to the secondary precepts of the natural law due to excessive passions, moral vices, corrupt customs, or sophistical arguments.{89} A legislator must take such blindness into account when attempting to govern in accordance with natural law.   

IV. Order in the Divine Mind and the Scientific Definition of Natural Law

A.) Natural Law as the Rational Creature’s Participation in the Eternal Law

We have seen that Sokolowski and Slade articulate what can be understood as the nominal definition of the natural law: the natural law is the ontological priority of ends over purposes and customs. With that nominal definition in place, how ought we to understand the real or scientific definition of natural law? In perhaps his most important statement on natural law, St. Thomas says:

The rational creature is subject to divine providence in a more excellent manner, because he himself participates in providence, providing for himself and others. Hence, in him, too, there is a participation in eternal reason through which he has a natural inclination to his due act and end. And the rational creature’s mode of participation in the eternal law is called natural law.  Hence, after the Psalmist (Psalm 4:6) has said, “Offer up the sacrifice of justice,” he adds, as if someone were asking what the works of justice are, “Many say, ‘Who is there to show us good works?’” In reply to this question he says, “The light of Your countenance, Lord, is imprinted on us”—as if to say, the light of natural reason, by which we discern what is good and what is evil. This has to do with natural law, which is nothing other than the imprint of God’s light within us. Hence, it is clear that natural law is nothing other than the rational creature’s participation in eternal law.{90}

We have in this text the real definition of natural law: the rational creature’s participation in the eternal law through the light of reason, which is an imprint of the divine light within us. As the real or scientific definition, this articulation manifests what is first in the order of being, but last in the order of discovery. It takes us from order in nature and order in the human mind to order in the divine mind, the causal origin, governor, and final end of all things.

The definition of the natural law as “nothing other than the rational creature’s participation in eternal law” enables us to develop critical points. When considering a given law in St. Thomas’s system (human, natural, Old, New), we should attend first to the legislative origin of the law. The pedigree of the agent of law provides the initial insight into the nature of the law being investigated. Because the natural law is the rational creature’s mode of naturally participating in the eternal law, which is divine in origin, the natural law is itself a divine law. Human law, by contrast, has its origin in human agents measured by natural law.

The eternal law is that through which God governs His creatures by directing them to their appropriate acts and ends in a manner fitting for them according to their nature, and Aquinas connects, or rather identifies, the eternal law with providence, and both with God’s wisdom. As Aristotle tells us, it is wisdom that enables one to order things well. St. Thomas says that the “eternal law is the plan (ratio) of divine providence.”{91} Providence, in its turn, is the “order of all things toward their end” as it “pre-exists” in God’s mind and in accordance with which God rules all things “sweetly.”{92} And to complete this triad of eternal law-providence-divine wisdom, Aquinas argues that God’s wisdom must be seen as both creative and governing:

It is through his wisdom that God is the creator of the totality of things, and he is related to those things in the way a craftsman is related to his artifacts. . . . God is also the governor of all the acts and motions found in each creature. Hence, just as the divine        wisdom’s conception has the character of an artistic conception or exemplar because all things are created through it, so too the divine wisdom’s conception has the character oflaw insofar as it moves all things to their appropriate ends. Accordingly, the eternal law is nothing other than the divine wisdom’s conception (ratio) insofar as it directs all acts and movements.{93}

When Aquinas discusses (natural) law, he sees it from the perspective of God as providential ruler of all created reality. He argues that God’s wisdom in the creation of a world of natures entails His providential governance of all things because His governance is understood in terms of the natural inclinations that flow from the substantial forms that enable entities to be and to seek their good, which is their proper perfection.{94} The eternal law shows that entities acting for their perfection according to their nature and from their own intrinsic principles of action are the expression of God’s wisdom, and our rational participation in this eternal law is the natural law.

Thus, God as creator does not just “see” each form or nature in isolation. He sees them altogether in their harmonious interrelation as they act for the sake of their perfections. He sees the Republic of Natures that serves as the metaphysical framework for natural law. Aquinas therefore identifies the eternal law, which governs all created reality by moving entities to their proper end, with the governing aspect of providence, for “government is the effect of providence.”{95} By linking the governing aspect of providence to the eternal law, Aquinas is able to show that all law, especially the natural law, participates in God’s wisdom, which includes His providential governance of creation. The formal cause of the natural law is therefore the eternal law of God insofar as we take part in it by reason; it is our reason’s natural participation in the providential governing wisdom of God in our own activities.

The legislator of the natural law, its efficient cause, is therefore God Himself, who promulgates it in the act of creation. Aquinas says that the natural law is “nothing other than the light of the intellect implanted in us by God, by which we know what should be done and what should be avoided. God gave this light and this law to man in creation.”{96} He also says that God “infuses” the law of nature in men in creation.{97} It is not that God creates an order of things that He “then” lifts into legal status, but rather that the order He creates simply is governed by His eternal providence; as the radically transcendent and provident cause of being (esse), God’s creation is governing, and His government is creating.

The material cause of natural law, its promulgation, is accomplished by God’s creative causality enabling and elevating our reason to share naturally in the linguistic disclosure of those goods or ends that are perfective of us as human persons and thus normative for our purposes and customs. God promulgates the natural law by enabling us to constitute a rule and measure of our actions in our rational encounter with the order of the natural world.{98} The “natural” in “natural law” refers to its mode of promulgation and reception, not to its legislative origin.{99} In the order of knowing, the natural law can be, and often is, promulgated even without advertence to its causal origin in God’s creative wisdom, which is first in the order of being but last in the order of discovery. In this respect, the natural law is similar to much of positive law for the majority of citizens subject to it, who often know the law without wisdom concerning its causal origins.

As for its final cause, the natural law is the manner in which God directs human agents to realize freely their natural end of virtuous friendships among themselves and between themselves and God, in whatever way friendship with God may be possible. The natural law governs human agents and enables them to be provident for themselves and for others by directing them toward happiness through the inculcation of virtue and the formation of friendships, thus contributing to the common good of the entire cosmos as the most favored parts of it.

In sum, the natural law is the way in which our reason naturally refracts God’s governing wisdom by disclosing those goods that are naturally right for us as human persons. As the ratio iuris embedded in the nature of things that God creates and that we see in the light of reason, natural law is the way we are made naturally to partake in the order “in” God’s mind by being provident for ourselves and for others. Because God is infinitely transcendent to the cosmos He creates and governs, because His immanence to his creatures flows from His radical transcendence, because He is wholly outside the cosmos as its extrinsic cause, He creates-governs things suaviter (sweetly in accordance with their nature), which means that He governs us freely in accordance with the imprint of divine wisdom that He grants us, the natural light of reason that discloses the natural law given to lead us to happiness in the truth. Order in the human mind is an imprint of the order of God’s wisdom, which directs all things to the glory of their First Cause and Final End.

B.) Natural Law and Virtue

If happiness in friendships with others in familial, political, and true religious societies is the final cause of the natural law, the perfection of our nature and thus the completion of the inclinations at the heart of the law of nature, then we must show how it is that we may achieve this end. How do we consistently and joyfully participate in these goods – of maintaining our being according to our nature, of familial and social life, and of the truth about God – toward which we are attracted by our rational nature through the creative-governance of God’s providence? Aquinas argues that “everything toward which man is inclined in accord with his nature belongs to the law of nature.” He argues that “every entity is naturally inclined toward action that is appropriate for it in light of its form, in the way that fire is naturally inclined to give warmth. Hence, since the rational soul is the proper form of man, every man has a natural inclination toward acting in accord with reason – which is just to act in accord with virtue.” He concludes that all the acts of virtue, insofar as they are the perfection of reason and its natural inclinations, “belong to the natural law, since the faculty of reason proper to each man dictates by nature that he act virtuously.”{100}

Aquinas strengthens this point in another text in which he says that “aptitude to virtue is in us by nature, but the completion (complementum) of virtue is in us through habituation or some other cause. Hence it is evident that virtues perfect us for following in due measure our natural inclinations, which pertain to what is naturally just. Therefore, to each determinate natural inclination is ordered some specific virtue.”{101} The natural, rational inclinations for human being, for social union in marriage, family, and polity, and for communion in the highest truth are the roots of societies oriented toward happiness. St. Thomas argues that the moral and intellectual virtues are the perfections of these natural inclinations. Each natural inclination has its correlative virtue, and developing this virtue as the perfection of our natural inclination belongs to that which is naturally just (the natural law). The moral “habits,” or what Simon calls the “existential readiness” to pursue good things consistently in a rational manner, are themselves the goods of virtue that perfect the natural inclinations by empowering us to reach the natural goods or ends toward which we are drawn.{102} The moral and intellectual virtues enable us to contribute more deeply to those societies – family, polity, and contemplative – toward which we are inclined by natural law and in which we find our own happiness.

The moral virtues of temperance, fortitude, and justice are brought to perfection in the intellectual virtues of practical and speculative wisdom, and all together they are the “virtues that perfect us for following in due measure our natural inclinations, which pertain to what is naturally just.” Thus, law and virtue are two sides of the same moral coin. Obeying the natural law and living by the virtues are not two different options for the moral life, but rather two dimensions of happiness in communion with others and with God. The natural law is the necessary and good foundation for the life of virtue. It is an authoritative signpost, a directive toward the life of virtue in friendship with others, a life that culminates in savoring the truth about God in activities of contemplative wisdom.  

Conclusion: A Trinity of Divine Laws: Natural, Old, and New

In closing, it is important to note that the eternal law aims principally at establishing friendship with God and that the natural law is the initial, natural human participation in the eternal law. As we have seen, Aquinas classifies a law as human or divine on the basis of its legislator. (1) The natural law, (2) the Old Law revealed to the Israelites, and (3) the New Law of “grace of the Holy Spirit given through faith in Christ” are therefore distinct species of (divine) eternal law because they are given by God.{103} They are hierarchically graded manifestations of the same eternal law, so the uplifting of human reason “begun” with the natural law is continued and specified by the Old Law and completed in the New Law of grace. The natural law is the beginning of what will eventually be revealed as a gradual road to friendship with God.

When, through God’s revelation, the natural law is taken not only as the law that is prior to our purposes, our positive laws, and the customs of our community, but also as the first of three divinely given laws (or rather the first of three disclosures of and participation in the eternal law) then the law of nature can more easily be seen to participate in the uplifting of human thinking and action. This divine pedagogy culminates in the gift of friendship with God through Jesus’s revelation and offer of grace. While the natural law aims to make us naturally good by directing us to live by truth, and while Moses spoke to God as a man would his friend, Jesus makes us His friends by speaking to us through the human nature united to the second person of the Trinity. The natural law can be said to lead to friendship with God insofar as it can be understood as a natural preparation for the coming of the Messiah of the Jews.

The natural law does not, by its native exigencies, aim at friendship with God understood as the unity of three divine, coequal, and coeternal persons, just as we do not have a natural desire for supernatural beatitude. As our natural desire for happiness is uplifted by grace into a supernatural participation in the triune life of God, so too the natural law itself is elevated into the economy of the Old Law and its fulfillment in the life of Christ. The natural law directs those human abilities of intellect and will that manifest our natural openness to God insofar as He can be known and loved as first cause and final end of the natural world, thereby refining those abilities that make us capax Dei. Therefore, the more we know and love God through the gift of the Holy Spirit given through faith in Jesus Christ, the more we participate in God’s trinitarian life through grace, the more we know and make known by our very lives that which is naturally good and the natural law that governs us toward it. For grace, as Aquinas says, heals, elevates, and imitates nature.{104}