Aquinas on natural law and the question of a Kantian misreading.

AuthorPintado, Patricia


The goal of this Article is to provide a brief introduction to some recent debate about what is and is not a Kantian reading of St. Thomas Aquinas's moral theory, in particular his account of natural law. (1) I will proceed in three steps. First, I will briefly review some of the key aspects of Aquinas's account of natural law, drawing primarily from the Summa Theologica. (2) Second, I will sketch the key points in a debate among some leading contemporary German-language scholars--namely, Georg Wieland, Ludger Honnefelder, and Martin Rhonheimer--regarding what is, and what is not, a Kantian distortion of Aquinas's understanding of natural law. Building upon this second section, I will summarize how Martin Rhonheimer's critique of L. Honnefelder and G. Wieland is useful in showing how an "autonomistic" interpretation of Aquinas's doctrine of natural law is tainted by Kantianism. Given that most of the bibliography is in German, I will rely mainly on two works by Rhonheimer that have been translated into English: first, Natural Law and Practical Reason: A Thomist View of Moral Autonomy and second, the chapter entitled "Practical Reason and the 'Naturally Rational'" in The Perspective of the Acting Person: Essays in the Renewal of Thomistic Moral Philosophy where he specifically addresses criticisms of the former work. (3)


    St. Thomas Aquinas's account of natural law is located within his treatise on law in Questions 90 to 108. (4) The first question of this treatise is programmatic, articulating fundamental aspects of Aquinas's teaching and providing a general definition of law. In Question 90, we learn that for Aquinas, "[1]aw is a rule and measure of acts" and "something pertaining to reason" which directs actions to the end. (5) "[A]ny inclination arising from a law," moreover, "may be called a law, not essentially but by participation." (6) He writes further that "universal propositions of the practical intellect that are directed to actions have the nature of law," (7) which seems to foreshadow what he will later say about the precepts or principles of natural law. (8) The remaining three articles of Question 90 complete his four-part definition of law: "[A]n ordinance of reason [ordinatio rationis] for the common good, made by him who has care of the community, and promulgated." (9) In an important and overlooked section in Article 4, Aquinas writes that "[t]he natural law is promulgated by the very fact that God instilled it into man's mind so as to be known by him naturally." (10)

    In the six articles of Question 91, Aquinas discusses various kinds of law. In Article 2, he treats the eternal law, which functions as somewhat of an exemplar for the rest. He defines it as "the very Idea of the government of things in God," (11) which could be understood as the Divine Mind, as considered under the aspect of how it governs all things. Our interest is in Article 2, where Aquinas asks whether there is a natural law in us. (12) In the sed contra, he quotes a gloss on a text from St. Paul's letter to the Romans 2:14, which considers how "the Gentiles, who have not the law, do by nature those things that are of the law." (13) The gloss reads: "Although they have no written law, yet they have the natural law, whereby each one knows, and is conscious of, what is good and what is evil." (14) This text seems to echo Aquinas's previously cited understanding of how natural law is promulgated by being known naturally. (15)

    The response in Article 2 is important. Here Aquinas discusses how

    the rational creature is subject to Divine providence in the most excellent way, in so far as it partakes of a share of providence, by being provident both for itself and for others. Wherefore it has a share of the Eternal Reason, whereby it has a natural inclination to its proper act and end: and this participation of the eternal law in the rational creature is called the natural law. (16) This last text is echoed at the conclusion of the response, which states: "[T]he natural law is nothing else than the rational creature's participation of the eternal law," (17) which is often taken to be Aquinas's definition of natural law.

    For several reasons, it might be better understood as less a definition of natural law than a statement of the relation of natural law to the eternal law. The first reason is that this question occurs within the treatise on law, which was introduced by the question on eternal law. The second is that Aquinas describes natural law as the rational creature's participation in the eternal law, only here and not in the other places in which he discusses natural law. The third reason is that the response of Article 2 also provides another candidate for the definition, namely that natural law is "the light of natural reason, whereby we discern what is good and what is evil." (18) Fourth, Aquinas elsewhere discusses the natural law with reference to the light of reason and usually with a reference to Psalm 4. He refers to natural law and/or natural reason along these lines, for example, in his commentaries on the Decalogue, (19) on the letter to the Romans, (20) and on the Psalms. (21) Because he will refer to it in Question 94, (22) we should also note that Aquinas teaches in Article 2 of Question 92 that law is a kind of precept or command concerning human acts, "a dictate of reason [dictamen rationis], commanding something." (23)

    The most important question in the Summa Theologica is Question 94, which treats the natural law in six articles. For our purposes, it suffices to refer only to Articles 1 and 2. In Article 1, Aquinas makes clear that natural law is not a habit "properly and essentially," because "natural law is something appointed by reason, just as a proposition is a work of reason." (24) "[N]atural law may be called a habit," however, in the sense that "the precepts of the natural law," or at least "the first principles of human actions," (25) are held habitually by synderesis. (26)

    In the much discussed Article 2, Aquinas looks at the precepts of natural law, asking whether they are several or only one. (27) For our purposes, we will note several key points. First, "the precepts of the natural law" are, in some sense, "self-evident principles" or propositions of practical reason. (28) Second, "the first principle of practical reason," which is "founded on the notion of good" (that which all things seek after) is "the first precept of law, that 'good is to be done and pursued, and evil is to be avoided."' (29) Third, "[a]ll other precepts of the natural law are based upon this: so that whatever the practical reason naturally apprehends as man's good (or evil) belongs to the precepts of the natural law as something to be done or avoided." (30) Fourth, "according to the order of natural inclinations, is the order of the precepts of the natural law." (31) Fifth, the following will belong to natural law based on this order of natural inclinations: "[W]hatever is a means of preserving human life, and of warding off its obstacles, ... sexual intercourse, education of offspring and so forth[;] ... to know the truth about God, and to live in society[;] ... to shun ignorance, to avoid offending those among whom one has to live, and other such things...." (32)

    In summary, Aquinas's view of natural law is founded upon an understanding of the...

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