Natural Law

Natural Law

Texts: C. E. Harris, The Ethics of Natural Law []


The Teleological World View (TWV)

The world, and all things in the world, have a function (purpose, end, goal (gr. telos)). (Variants of this theory assume only that humans and other living creatures have telos).

A Christian Philosopher, and the Doctor of Church, St. Thomas Aquinas (1225‑74) attempted to provide interpretation of the Holy Scripture in light of philosophical insights of the great Greek philosopher, Aristotle (383‑322 B.C.). Both Aristotle and Aquinas assume that (TWV) is true. To support this view Aquinas assumes that world is both intelligently designed and created in accordance with the Divine Plan.

It is an open question whether an atheist can also assume that the Teleological World View is true. Many physicalists and materialists (students of Newton, Kepler, and Galileo) would reject TWV. They argue that since everything is a result of purely physical causes, nothing has telos.

Suppose, however, that at least living creatures, especially humans, have telos a proper purpose. Given this assumption, we can develop an ethical theory.

Positive (human) Law vs. Natural Law

Augustine distinguishes two kinds of law, the one eternal, the other temporal, which he calls human... These particular determinations, devised by human reason, are called human laws, provided that the other essential conditions of law be observed... (Aquinas, Q91, art 3)

To wit, human (positive) law is what we design to guide our action. Aquinas notices that, since our intellects are limited, our laws are imperfect in many respects. For example, human laws sometimes fail to proscribe all bad things (Q91, art. 4).

Aquinas thinks also that, for each human being, our destiny (goal) is to flourish and be fully happy. But he observes also that our natural abilities are insufficient to bring about our destiny, we have insufficient skills to guarantee that we will be happy. As he observes:

man is ordained to an end of eternal happiness which exceeds man's natural ability, . . . therefore it was necessary that, in addition to the natural and the human law, man should be directed to his end by a law given by God. (ibid.)

Aquinas calls this God's law the Natural Law. NL is a set of principles that guide the behavior of all rational beings in accordance with our proper function. Those principles are independent of any human law and depend only on the nature of humans (in other words, on our essence or proper function).


NLT1: An action, A, is morally right iff A is consistent with the nature (essence) of a human (or a living) being.

The nature (essence) of a human being encompasses all of our relevant proper purposes. Hence, there is another way to state the main principle of NLT:

NLT2:An action, A, is morally right iff A is consistent with all relevant proper purposes of a human (or a living) being.

Aquinas accepts an Aristotelian concept of a human being as a rational animal. That is, our essence (nature), consists in the fact that we are both rational and biological beings. This fact points to two different sets of requirements that we must fulfill. First, Aquinas thinks that all actions that develop us as rational beings of intellectual nature are morally right. As he observes:

"the rational soul is the proper form of man, there is in every man a natural inclination to act according to reason; and this is to act according to virtue. Consequently, considered thus, all the acts of the virtues are prescribed by the natural law, since each one's reason naturally dictates to him to act virtuously. ... For many things are done virtuously, to which nature does not primarily incline, but which, through the inquiry of reason, have been found by men to be conducive to well‑living...." (Q93, art. 3)

All actions that harm our rational nature (or are contrary to it in some other way) are morally wrong.

In addition, actions that sustain us as biological organisms are also morally right. By extension, actions that harm us as biological organism are wrong. As he observes:

Temperance is about the natural concupiscences of food, drink and sexual matters, which are indeed ordained to the common good of nature, just as other matters of law are ordained to the moral common good. (Q93, art. 3)

Aquinas and many NL theorists assume that we are created in God's image. We must remember that they assume also that God is maximally (or all‑)good, maximally powerfull, and all‑knowing. These assumptions have profound implications. Most fundamentally, God never creates anything bad, and never aims at anything bad. At most, God allows for bad things to happen and only if there is a sufficient reason for it. (Notice what we earlier said about the argument from evil and the superfluous evil.)

SUPLEMENTARY PRINCIPLES: Can we ever take a life of a person. Traditional versions of (NLT) tried to solve the problem by the means of one of the folowing principles:

The Principle of Forfeiture (PF): If X threatens an innocent human life (i.e., violates the principle concerning the protection of life), X forfeits his (her) right to life. Thus, killing in necessary self‑defense is morally permissible.

Many contemporary proponents of NLT reject (PF). They think that this principle cannot be reconcile with the doctrine of the sacnctity of human life. Notice, just like it is not in God's nature to directly bring about something bad (for God is all good), it is not in our nature (essence) to aim at anything bad. At most, we can allow that bad things happen and only if there is a sufficient reason for that. This is known as

The Principle of Double Effect (PDE): A person may lawfully perform an action from which two effects will follow, one bad, and the other good when four conditions obtain:

1. The act itself must be morally good or at least indifferent.

2. The agent may not positively will the bad effect but may merely permit it. If he could attain the good effect without the bad effect, he should do so.

3. The good effect must flow from the action at least as immediately (in the order of causality, though not necessarily in the order of time) as the bad effect.

4. The good effect must be sufficiently desirable to compensate for the allowing of the bad effect. [Adopted from the New Catholic Encyclopedia]