3. Natural Law: Its Central Meaning and Character
Thomas teaches that all created realities “participate” in the eternal law. But they do so differently, in accordance with their natures. Nonrational beings participate in the eternal law in a purely passive way insofar as from it they receive an “impression” whereby “they have inclinations toward their proper acts and ends.”12 The eternal law is “in” them inasmuch as they are ruled and measured by it.13 But human persons, inasmuch as they are intelligent, rational creatures, participate actively in the eternal law, and their active, intelligent participation is precisely what the natural law is.14 The eternal law is “in” them both because they are ruled and measured by it and because they actively rule and measure their own acts in accordance with it. It is thus “in” them properly and formally as “law.” Contrasting the different ways in which nonrational and rational creatures participate in God’s eternal law, Aquinas says: “Even nonrational animals participate in the eternal ratio in their own way, just as does the rational creature. But because the rational creature participates in it by intelligence and reason (intellectualiter et rationaliter), therefore the participation of the eternal law in the rational creature is properly called law: for law is something pertaining to reason.… But in the nonrational creature it is not participated in rationally; hence it cannot be said to be law [in the nonrational creature] except by way of a similitude.”15
Natural law, as it exists in the rational creature, is entitatively distinct from the eternal law that exists in God, the superintelligent Creator. But it is not something “other than” the eternal law. It is this eternal law itself mediated to or shared by the rational creature.16 Natural law characterizes both the nobility of the rational creature as the being created in the image of God and the great love that God has for the rational creature, whom he wills to share actively in his own provident wisdom.
Thomas clarifies the way that the eternal law is “in” the rational creature when he considers the position, held by many of his medieval predecessors, that the natural law is a power or a habit, in particular the habit of synderesis or of the first principles of practical reasoning.17 He grants that natural law may, in a secondary and derived sense, be regarded as a habit insofar as the judgments of practical reason that together go to constitute it are habitually kept in mind. But in its proper sense, natural law is not a habit, nor is it a power. Rather, it is a reality brought into being (constitutum) through reason; it is a work of human intelligence as ordered to action (ratio practica), just as a proposition of the speculative intellect is an achievement of human intelligence as ordered to knowing for the sake of knowing. Natural law, therefore, is something that we ourselves naturally bring into being by the spontaneous exercise of our own intelligence as ordered to action. It is something that we bring into being by our doing (what Thomas calls a quod quis agit), not something enabling us to bring something into being by our own doing (what he calls a quo quis agit).18
As such and properly, then, natural law is for St. Thomas an achievement of practical reason. It consists of a body or ordered set of true propositions formed by practical reason about what-is-to-be-done.19 But what are these propositions, and how do they constitute an ordered set?
Thomas begins to address this issue in the important second article of question 94 of the Prima Secundae of his Summa theologiae. In this article, he is concerned with the “starting points” or “first principles” of natural law, the first set of practical propositions or precepts that go to make it up. In this article, he begins by making an important analogy between the precepts of natural law, which pertain to reason as ordered to action (ratio practica), and the first principles of demonstration, which pertain to reason as ordered to speculative inquiry or knowledge for the sake of knowledge (ratio speculativa). He says that just as being is the first thing that our intellect grasps with regard to its knowledge of reality, so good is what is first of all grasped by our intelligence as directed to action. He then declares: “Therefore, the first principle in practical reason is that which is founded upon the meaning (ratio) of the good, which meaning is, the good is that which all things desire. Therefore, this is the first precept of [natural] law, namely, that good is to be done and pursued, and evil is to be avoided. And upon this [precept or ‘proposition’ of practical reason] are based all other precepts of natural law, namely, that all those things belong to natural law that practical reason naturally grasps as goods to be done [or evils to be avoided].”20
Continuing, Thomas says that “good” has the meaning of an end, whereas “bad” has the opposite meaning. It thus follows that “reason naturally apprehends as goods, and consequently to be pursued in action, all those things to which man has a natural inclination, and things contrary to them [reason naturally apprehends] as evils to be avoided.”21
It is most important here to note that Thomas does not say that these “natural inclinations” constitute natural law. Rather, he is saying that the real goods of human existence to which human beings are naturally oriented are grasped “naturally” — i.e., nondiscursively — by human reason as the “good” that is to be done and pursued. Practical reason apprehends in these goods the “ends” or “points” of human choices and action. To put matters another way, the basic practical principle that good is to be done and pursued, and that its opposite, evil, is to be avoided is specified by identifying real goods of human persons. According to Thomas, there exist within us “natural inclinations” dynamically directing us toward specific aspects of human well-being and flourishing, and our practical intelligence “naturally” apprehends as good, and therefore to be pursued in human choice and action, the realities to which these natural inclinations direct us. When he says that practical reason “naturally” apprehends the goods to which human beings are naturally inclined, Thomas means that there is no need for discursive, syllogistic reasoning in order for us to know them as good. Knowledge of these goods is not innate, but it is direct and nondiscursive, given human experience.
But what are our “natural inclinations” and the basic human goods or aspects of human well-being corresponding to them? In q. 94, a. 2, Thomas distinguishes three levels of basic, natural inclinations and basic human goods. On the first level, there is in us a natural inclination to the good in accordance with the nature that we have in common with all substances. The good to which we are naturally inclined at this level is that of being itself, and since, as Thomas elsewhere notes, the being of living things is life itself,22 the relevant human good here is life itself. At another level, there is in us a natural inclination “to more special goods according to the nature” we have “in common with other animals.” The relevant good here is the union of male and female and the handing on of new life and the education of human persons. Finally, there is in us, Thomas says, an “inclination to the good according to the nature of reason, which is a nature proper to man: thus man has a natural inclination to know the truth about God, and to live in society; and in this respect whatever pertains to this inclination belongs to natural law, for example, that man avoid ignorance, that he not give offense to others with whom he must live (conversari), and other such things.”23 In other words, the relevant human goods to which this inclination points us are such goods as knowledge about God, fellowship and friendship with other persons, and the like.
The list of basic human goods given by Thomas in this article is not intended by him to be taxative or exhaustive; it is rather an illustrative list, as is indicated by the fact that he uses such expressions as “and the like” (et similia) and “of this kind” (huiusmodi) in speaking about the goods that he names. Moreover, in the very next article Thomas explicitly says that “there is a natural inclination in every human being to act in accord with reason. And this is to act in accord with virtue.” Thus, here the good to which we are naturally inclined is the good of virtue.24
It seems that one can legitimately say, on the basis of q. 94, a. 2 of the Prima Secundae, that the goods to which we are naturally inclined, when grasped by practical reason, serve as starting points or principles of practical reason, of