It is not uncommon to run across the term “natural law” in Catholic journals and newspapers. Frequently, the context is a discussion of hot-button moral issues in the culture war, such as abortion, euthanasia, homosexuality, birth control, and so-called “end-of-life decisions.” It is encouraging to see the Holy See referring to the natural law frequently as of late, making these instances in the press more frequent. The Holy Father has made a serious effort to make this shibboleth of Catholic orthodoxy more widely known.
But what is the “natural law”? What is its origin? What is its purpose? I have found that many Catholics are entirely ignorant of the concept and will therefore get very little out of these references in the Catholic media.
These considerations make it worthwhile to give an overview of this all-important topic.
According to St. Thomas, whose thought on the subject we will merely introduce, the natural law is “nothing else than the rational creature’s participation in the eternal law” (ST I-II, Q. 91, A. 2.). His natural law theory holds that the eternal law as it is in the mind of God is knowable in a limited degree by our finite human intellects. That is to say, not only is there a rule or order in nature, but this order or rule is accessible to the human intellect.
In the historical background to the natural law theory of St. Thomas, we have the Catholic Deposit of Faith (Scripture and Apostolic Tradition), as well as the philosophical tradition of Roman Stoicism.
The Bible and Tradition witness to the presence of a law of God in which men participate by their rational nature. A classic Biblical reference to the natural law is Rom. 2:14, where St. Paul compares the Gentiles’ knowledge of God through nature with the Jews’ knowledge of God through revelation: “For when the Gentiles, who have not the law, do by nature those things that are of the law; these having not the law are a law to themselves.” Sources of apostolic Tradition, such as the writings of St. Augustine, St. Basil, and St. John Damascene also contribute to St. Thomas’ reasoning, and are explicitly referenced in the Summa. The thinking of Greek and Roman philosophers, especially the Roman Stoics (among whom, Julius Caesar is referenced — Cf. ST I-II, Q. 91, A.) also contributes. The works of Aristotle, the medieval Aristotelian philosopher Boethius, and the Church Law of his day (the Decretals) also come into the saint’s explanation.
What theologians call “the remote source” (that from which it originally comes) of natural law is the Eternal Law, which is God’s Providence as governing creation. Its proximate source (where we find it) is human reason — unaided human reason. God ordered all of creation to the achievement of certain ends and put in each creature the means by which it could attain its end. Man, a being endowed with reason, has in himself the means by which he can tend to the end proper to a rational creature. Included among these means is the natural law.
The natural law is a system built upon principles of right and wrong. The secondary principles are derived from the primary ones. In the words of St. Thomas, “the first principle of practical reason is one founded on the notion of good, viz. that ‘good is that which all things seek after.’ Hence this is the first precept of law, that ‘good is to be done and pursued, and evil is to be avoided.’ All 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” (ST I-II, q. 94, a 2).
Obviously “do good, avoid evil” is not a sufficient guide for all human activity! But it’s a good start. Perceiving the goodness of the natural inclinations of his rational nature, man’s practical intellect treats them as the principles from which to formulate the more specific precepts of the natural law, the first of which is based on man’s tendency to self preservation. This first principle is “preserve life.” Here we see that the Fifth Commandment, “Thou shalt not kill,” is really part of the natural law. God did not have to reveal it on Mount Sinai, but He did so as a mercy. (The same is true of all of the commandments of the Decalogue, except the specification of the Sabbath as a day to keep holy. God had to reveal that in his Positive Law.)
The movement from general principles and precepts of the natural law to specific human acts is full of difficulties because of the complexity of human action. It could be that more than one of the secondary principles of natural law comes into play in a given instance, and it could be that the contingencies and complex processes of secondary causality make the right course of action anything but easy to conclude. At the end of this article, I will illustrate how such a complexity can enter into the field of medical ethics, and in a relatively simple case (if that makes sense!).
Only for Catholics? Some would have it that the natural law is a concept of Catholic moral theology, and therefore not something that all men are bound to observe.
Nothing could be further from the truth.
The very notion of “natural law” implies something independent of God’s supernatural revelation. The Catholic Faith is a supernatural revelation, but the natural law is something common to all men.
To the Catholic who would challenge the universal application of the natural law (as many liberals do), I would point out the above-cited testimony of St. Paul: “when the Gentiles, who have not the law, do by nature those things that are of the law; these having not the law are a law to themselves” (Romans 2:14). This is generally interpreted to mean that those who did not have the benefit of the revelation of the Old Testament (specifically the Mosaic Law) were still naturally endowed by their Creator with consciences capable of judging good and evil. The next verse goes on to say that these pagans show “the work of the law written in their hearts, their conscience bearing witness to them, and their thoughts between themselves accusing, or also defending one another.”
This tradition was upheld even at Vatican II. Gaudium et Spes (No. 16) makes mention of this law written on the heart: “In the depths of his conscience, man detects a law which he does not impose upon himself, but which holds him to obedience. Always summoning him to love good and avoid evil, the voice of conscience when necessary speaks to his heart: do this, shun that. For man has in his heart a law written by God; to obey it is the very dignity of man; according to it he will be judged.”
The conciliar text footnotes passages from St. Thomas’ Summa Theologica (II-II, q. 32, a. 5 ad 2; and q. 66, a. 2) where the Angelic Doctor affirms that all human beings, not only Catholics, know the eternal law of God to the extent that they know the universal principles of the natural law. So the council fathers clearly had in mind the universality of the natural law. The teaching is not unique to St. Thomas: “The general teaching of theologians is that the supreme and primary principles [of the natural law] are necessarily known to every one having the actual use of reason” (The Catholic Encyclopedia, “Natural Law.”)
To the non-Catholic who may claim that natural law does not bind him because it is “Catholic,” I would offer the following:
- “Do good and avoid evil” — the first precept of the natural law — is found in the legal codes, philosophical works, religious books, and literary monuments of all civilizations, ancient and modern.
- Many of the secondary precepts of the natural law — e.g., prohibitions of murder, theft, and adultery — are found in those same historical records, such as the Code of Hammurabi, the ancient Babylonian legal code.
- Much of modern literature, which seeks to be “value free,” is filled with stories of the bitterness of guilt which visits those who violate their consciences in matters of the primary and secondary precepts of the natural law.
In short, the common experience of mankind acknowledges the universality of the natural law.
Evangelical Importance. The natural law is a basis from which we can reach out to the non-Catholic. We begin with what we have just asserted, viz., that the natural law applies to all men and that all have a knowledge of its fundamental precepts. From there we see that the natural law is something integrally part of the Catholic moral life. Since all men know these principles in some degree, they will see the basic moral teachings of the Church as good and reasonable. Of course, sin darkens the intellect and weakens the will, so it can and often does muddle this process. But that is no reason to quit before you begin. We must confidently assert that all men have the natural law on their hearts. For this reason, the natural law provides a strong foundation from which to begin in our conversations with non-Catholics.
Building upon that, we acknowledge, with St. Thomas and the generality of theologians, that there will be confusion about the application of the secondary principles of the natural law. As St. Thomas teaches in the Summa Contra Gentiles, those who desire knowledge also desire to flee ignorance (III, 50, 6) and that which is imperfect desires to be perfected (III, 50, 2). Therefore, those in pursuit of greater clarity, knowledge, and understanding of the law that is written in their hearts — if their pursuit be accompanied by a resolute good will — will see the reasonableness of the moral teachings of the Catholic faith which clarify the secondary precepts of the natural law. This, of course, could be a grace leading to their conversion.
Medical Ethics Example. Now for that example of how the secondary precepts of the natural law can become complex in their application: It could be that someone in a hospital has a condition which would be worsened by the intake of fluids, such as kidney failure or congestive heart failure. Prudent medical practice, applying the principle “preserve life,” could dictate that such a patient be very restricted in his fluid intake (at least until diuretics or dialysis can be administered). These conditions also cause great thirst. Now, the natural law puts in the patient an instinct of self-preservation, telling him it is better to drink than not to drink. However, the known medical fact that hydration at this time could be detrimental, must restrain the impulse of patient to drink. This is so because of the principle which says that life should be maintained and death avoided is on the side of restricting fluid intake. In this example we not only see an illustration of the secondary principle of natural law (preserve life), but we see an example of how (at least in the patient’s mind), the precise application of the law can be fraught with danger as, in his mind, drinking large quantities of water is reasonable.