Natural Law Theory


I.          Introduction: Two Species of Natural Law Theory.

A.        Natural Law as a Theory of Morality.  At the outset, it is important to distinguish two kinds of theory that go by the name of natural law.  The first is a theory of morality that is roughly characterized by the following theses.  First, moral propositions are the bearers of objective truth-value; that is, moral propositions can be objectively true or false.  Second, standards of morality are in some sense derived from, or entailed by, the nature of the world and the nature of human beings. 


B.                Natural Law as a Theory of Law.  But there is another kind of natural law theory having to do with the relationship of morality to law.  According to natural law theory of law, there is no clean division between the concepts of law and morality.  Though there are different versions of natural law theory, all subscribe to the thesis that there are at least some laws that depend for their “authority” not on some pre-existing human convention, but on the logical relationship in which they stand to moral standards. 


II.          Aquinas’s Analysis of Law.  Aquinas takes the notion of law to be central to all normative practices – not just legal practices – including morality; and he gives a general analysis of the concept as it figures in all forms of law (again, including the natural law).  The theory can be summarized in the following analysis:

A rule R is a law if and only if 1) R is a directive of reason; 2) R is aimed at the common good; 3) R is promulgated; 4) R requires or prohibits certain actions; 5) R is backed by coercive power; and 6) R is intended to be obeyed. 


III.         Types of Law.  On Aquinas’s view, there are four types of law: eternal, divine, natural, and human. 

A.                Eternal law.  The set of timeless truths that govern the movement and behavior of all things in the universe, including non-human things. 

B.                 Natural law.  That portion of the eternal law that applies to the behavior of human beings.

C.                Human law.  Law that “purports” to have a human source.

D.               Divine law.  The law that pertains to “our last end” – which refers to our ultimate fate after divine judgment.  Presumably,


IV.        A Brief Summary of the Natural Law.  Human nature (it is human nature to which natural law is natural; the laws of nature to which Aquinas refers derive from human nature) is free and rational.  As free and rational beings, the human will can be moved to act only by reasons.  Accordingly, since rational beings are naturally disposed to pursue the good, the first precept of natural law is to pursue what is good and avoid what is bad.  All other precepts of natural law can be derived from this foundation.  

On Aquinas’s view, there are three kinds of good that human nature pursues:  1) those goods that a human being shares with all other substances, such as, for example, the preservation of his or her being in accordance with his or her nature; 2) more specific goods that a human being shares with other members of the animal community, such as the desire to mate; and 3) goods that are valued because of a human being’s capacity for rationality, such as a desire to find out the truth about God and morality and the desire to live in society. 


V.        The Relationship between Human Law and Natural Law.  Here’s the way Aquinas describes it: “As Augustine says, ‘that which is not just seems to be no law at all’; wherefore the force of a law depends on the extent of its justice.  Now, in human affairs a thing is said to be just from being right according to the rule of reason.  But the first rule of reason is the law of nature, as is clear from what has been stated above.  Consequently, every human law has just so much of the nature of law is it is derived from the law of nature.  But if, in any point, it deflects from the law of nature, it is no longer a law but a perversion of law.”

As Blackstone puts the point: “This law of nature, being co-eval with mankind and dictated by God himself, is of course superior in obligation to any other.  It is binding over all the globe, in all countries, and at all times: no human laws are of any validity, if contrary to this; and such of them as are valid derive all their force, and all their authority, mediately or immediately, from this original.”  There are two interpretations of these passages – each suggesting a different relationship between law and morality. 


 A.     The Traditional Descriptive Interpretation: Necessary Moral Constraints on What Counts as Law.  On this traditional interpretation, it is a conceptual truth that no norm that is inconsistent with the natural can count as a law (in any legal system). 


This version of natural law has traditionally been rejected on the strength of Austin’s hangman argument.  As Austin puts it: “Now, to say that human laws which conflict with the Divine law are not binding, that is to say, are not laws, is to talk stark nonsense.  The most pernicious laws, and therefore those which are most opposed to the will of God, have been and are continually enforced as laws by judicial tribunals.  Suppose an act innocuous, or positively beneficial, be prohibited by the sovereign under the penalty of death; if I commit this act, I shall be tried and condemned, and if I object to the sentence, that it is contrary to the law of God, who has commanded that human lawgivers shall not prohibit acts which have no evil consequences, the Court of Justice will demonstrate the inconclusiveness of my reasoning by hanging me up, in pursuance of the law of which I have impugned the validity.  An exception, demurrer, or plea, founded on the law of God was never heard in a Court of Justice, from the creation of the world down to the present moment.”

B.            The Contemporary Normative Interpretation: Necessary Moral Constraints on What Should Count as Law.