Chapter 7. Deontological Theories: Natural Law
Section 4. Natural Law Theory


With this theory actions in conformity and support of natural laws are morally correct.  A simple summary would be :

What Is Consistent with the Natural Law Is Right and What Is not in keeping with the Natural Law Is Wrong

NOTE: This is NOT what is natural is morally correct and what is unnatural is morally wrong.  The focus is on the natural LAWS and not simply natural acts.  Natural Law Theory supports doing unnatural deeds such as surgery for the sake of realizing a restoration of health and the prolongation of human life which are each consistent with the natural drives of organisms: survival.

VIDEO at Natural Law Theory

In this view humans have reasoning and the Laws of Nature are discernable by human reason.   Thus, humans are morally obliged to use their reasoning to discern what the laws are and then to act in conformity with them.

Humans have a natural drive to eat, drink, sleep and procreate.  These actions are in accord with a natural law for species to survive and procreate.  Thus activities in conformity with such a law are morally good.  Activities that work against that law are morally wrong.  As an example consider that to eat too much or too little and place life in jeopardy is morally wrong.

Two types of Natural Law Theory:

Natural Law Theory can be held and applied to human conduct by both theists and atheists.  The atheist uses reason to discover the laws governing natural events and applies them to thinking about human action.  Actions in accord with such natural law are morally correct.  Those that go against such natural laws are morally wrong. 

For the theists there is a deity that created all of nature and created the laws as well and so obedience to those laws and the supplement to those laws provided by the deity is the morally correct thing to do.

For atheists there is still the belief that humans have reasoning ability and with it the laws of nature are discernable.  For atheists who accept this approach to act in keeping with the laws of nature is the morally correct thing to do. 

What are the laws of nature that provide guidance for human actions?  These would include: the law of survival, the natural action for  living things to maintain themselves and to reproduce, etc..

It is a major problem for this theory to determine what exactly those laws are and how they apply to human circumstances.

READ about this theory here>



This is from wikipedia

The Roman Catholic Church understands natural law to be immanent in nature; this understanding is in large part due to the influence of Thomas Aquinas (1225-1274 A.D.), often as filtered through the School of Salamanca.

It understands human beings to consist of body and mind, the physical and the non-physical (or soul perhaps) and that the two are inextricably linked. It describes human persons as being inclined toward the good. There are many manifestations of the good that we can pursue, some, like procreation, are common to other animals, while others, like the pursuit of truth, are inclinations peculiar to the capacities of human beings.

  • Drunkness is wrong because it injures the health and worse, destroys one's ability to reason, which is fundamental to man as a rational animal.
  • Theft is wrong because it destroys social relations, and man is by nature a social animal.

Martin Luther King, Jr. invoked the natural law in his "Letter from Birmingham Jail", stating that the man-made (positive) laws that he broke were not in accord with the moral law or the Law of God (natural law).

Hugo Grotius based his philosophy of international law on natural law. In particular, his writings on freedom of the seas and just war theory directly appealed to natural law. About natural law itself, he wrote that "even the will of an omnipotent being cannot change or abrogate" natural law, which "would maintain its objective validity even if we should assume the impossible, that there is no God or that he does not care for human affairs." (De iure belli ac pacis, Prolegomeni XI). This the famous argument etiamsi daremus (non esse Deum), that made natural law no longer dependent on theology.



The theory also utilizes the Principle of the DOUBLE EFFECT whereby some morally incorrect result  or evil  is morally acceptable provided that those who brought it about  entered into actions  with the only purpose(s)  being to bring about some morally good end.  Thus, a surgeon is not morally blameworthy if a person dies under the care of the surgeon provided that the surgeon performed the surgery following the standards of care with the sole intention of improving the condition of that person.

The theory also utilizes the Principle of the DOUBLE EFFECT:

Explanation and illustration from WIKIPEDIA


DOUBLE EFFECT This set of criteria states that an action having foreseen harmful effects practically inseparable from the good effect is justifiable if the following are true:

  • the nature of the act is itself good, or at least morally neutral;
  • the agent intends the good effect and does not intend the bad effect either as a means to the good or as an end in itself;
  • the good effect outweighs the bad effect in circumstances sufficiently grave to justify causing the bad effect and the agent exercises due diligence to minimize the harm.[2]

Examples In Medicine

·        The principle of double effect is frequently cited in cases of pregnancy and abortion. A doctor who believes abortion is always morally wrong may still remove the uterus or fallopian tubes of a pregnant woman, knowing the procedure will cause the death of the embryo or fetus, in cases in which the woman is certain to die without the procedure (examples cited include aggressive uterine cancer and ectopic pregnancy). In these cases, the intended effect is to save the woman's life, not to terminate the pregnancy, and the effect of not performing the procedure would result in the greater evil of the death of both the mother and the fetus.[4][5][6]

·        In cases of terminally ill patients who would hasten their deaths because of unbearable pain, or whose caregivers would do so for them (euthanasia, medical aid in dying, etc.), a principle of "double effect death" could be applied to justify the deliberate administration of a pain-killer in potentially unsafe doses—not in an attempt to end life but to relieve the pain suffered as it is considered harmful to the patient. The U.S. Supreme Court has voiced support for this principle in its deliberations over the constitutionality of medical aid in dying.[7]





Application of the theories to one behavior:  HOMOSEXUALITY

Under the Natural Law Theory two people of the same sex interacting to produce orgasms will be morally good or bad depending on whether or not such actions are in accordance with natural laws or not.

Atheistic Natural Law Theory:

If there are species on earth in which members of the same sex physically interact to produce physical pleasure then homosexual couplings amongst humans would be morally good. The purpose of orgasms would be more than to produce offspring.

PROBLEM: the physical record may not be all that clear and open to interpretation. There is evidence of same sex couplings in species other than human. How many cases or species are needed to conclude that such behavior is natural among mammals and fulfilling a basic physical drive in a non-harmful manner to the species is what is debatable.

Theistic Natural Law Theory:

God made Nature. God made the Natural Laws. God made humans. God gave humans reason by which they are to learn of the natural laws. God also provides revelation concerning god's will and wishes. In the scriptures there are passages dealing with human matters and they are interpreted to have been given as a guide for the moral life. So in addition to the physical universe which is provided for the study of humans there is also the word of god.

PROBLEM:  The Sacred Scriptures of the world's religions need to be interpreted as to their meaning and application. Not all will agree as to what the best interpretation might be. Consider the example below that is of great importance to a large number of people because depending on how certain biblical passages are understood has grave implications for a large number of people who either are not heterosexual or who practice sexual actions other than for procreation.

There is a passage in the bible where Onan is condemned because he did not go into the tent of his dead brother's wife and have sex with her so as to produce more children. (see two accounts below) . At that time it was the custom in the tribe that when a man died his brother would be responsible for his wife and take her as another wife in order to continue the tribe. Onan went into the tent had sex with the dead brother's wife but pulled out of her and spilled his semen on the ground. He was condemned for doing so.


A. Was Onan condemned for entering into sex for a purpose other than having children? If so then all sexual acts other than intercourse between a man and a woman who are married and preparing to have children would be immoral. These acts would include: Premarital sex, extra marital sex, masturbation, homosexuality, oral sex, anal sex, use of birth control.

B. Was Onan condemned for not being willing to father children by his dead brother's wife? If so, then sexual acts entered into for a purpose other than procreation would be morally acceptable.

There are many people who take each of these possible interpretations of the passage. Here are two commentaries.

 Genesis 38:6-9 -- The sin of Onan:

This passage describes how Tamar's first husband Er was killed by God because he was wicked. Under ancient Jewish tradition, Er's brother Onan was required to marry and engage in sexual intercourse with Tamar. Widows were not asked whether they wanted to remarry. In many cases, the woman would have experienced the sexual activity as a form of rape -- something required by tribal tradition which they had to endure. Similarly, nobody consulted the widow's brother-in-law about his wishes in the matter.

Their first son would be attributed to Er. Because any offspring would not be considered his child, Onan decided to use a common and relatively ineffective contraceptive technique to prevent conception. He employed "coitus interruptus". That is, he disengaged from Tamar just before he ejaculated, and "spilled his semen on the ground." (NIV) God was displeased at this action and killed Onan also -- presumably because he refused to follow Jewish tradition.

This passage was used until recent decades by some Christian groups who maintained that Onan's sin was actually masturbation. The term "Onanism" was coined as a synonym of masturbation. This interpretation is no longer in common use.


Onan was the middle of the three children of Judah, son of Jacob and father of the tribe which eventually produced both Kind David and Jesus. His older brother died without producing an heir. In those days, it was customary for the younger brother to take his deceased brother's wife and provide that brother with an offspring. So, Judah, Onan's father, ordered him to do such.

According to the account, Onan realized that his biological son, produced in this manner, would not be considered his own. If Onan provided his older dead brother with a son, that child would inherit both the seat of chief of the tribe as well as the oldest's portion of the estate. It meant that Onan would be inferior to his own biological child. It also meant that Onan would lose "financially."

The laws of inheritance in those days required that the older brother receive a double portion. This meant that if Onan provided his brother with an heir, Judah's holdings would be divided four ways, with two fourths (or one half) going to this child while Onan would only receive one fourth. However, if Onan retained his status as oldest surviving son, the inheritance would be divided three ways, with Onan receiving two of those thirds or about one and a half times more.

According to the scriptural account, Onan insured his failure by practicing the most ancient form of birth control known, premature withdrawal. For this, God struck him dead.

The account says that Tamar was the name of the wife and her dead husband committed some sin so grave that God killed him, although it doesn't specify the sin. Now, her husband's younger brother commits a sin, with her, and he is struck down by God. This man sent to her to provide her dead husband with an heir, has sexual relations with her. He pulls out before ejaculation, spills his seed on the ground and dies on the spot.





Historical Course of Natural Law Theory  from Theistic to Atheistic

 by Andrew Sandlin  at  


Thomas Aquinas on Natural Law


A Christian Reformed Critique

  Religion and Morality:


Other Sources Concerning Natural Law Theory: 

Encylopedia of Philosophy - Natural Law -
Definition and explanation of natural law theory with bibliography.

Natural Law and Natural Rights -
Paper by James Donald about history, theory, and prediction for natural rights and natural law with bibliography.

Elements of Natural Law and Politics -
Full text of a treatise by Thomas Hobbes on natural law.

Jurisdictionary - Search for Natural Law -
Examination of American jurisprudence through natural law theory.

The Natural Law by Heinrich A. Rommen -
The Natural Law, a study in legal and social history and philosophy.


The Case For and Against Natural Law -
Lecture by Russell Kirk for the Heritage Foundation presenting conflicting views of natural law.

Haines: The Revival of Natural Law Concepts -
Study of the establishment and interpretation of the limits on legislatures.

Natural Law: A Reformed Critique -
Examiniation of natural law by Peter J. Leithart found in Premise.

Huig de Groot (Hugo Grotius) -
Hugo Grotius 1583-1645, founder of natural law theory.

Natural Law and Will -
John Kilcullen's examiniation of natural law in Descartes and Ockham.


The Non-Absurdity of Natural Law -
Defense of natural law theory and natural rights against egoist attacks by Wendy McElroy from The Freemason.

Aquinas on Natural Law -
Summary of Thomistic view of natural law.

Natural Law Frigate -
Discussion forum and live chat devoted to natural law.

Natural Born Lawyers -
Article by J. Budziszewski on natural law with links to purchase related books.

Darwin and Natural Law -
Search for a darwinian science of ethics.


Encarta Encyclopedia Article - Natural Law -
Encarta summary on history of natural law.

Proceed to the next section of the chapter by clicking here>> section.

© Copyright Stephen O Sullivan and Philip A. Pecorino  2002. All Rights reserved.

Return to:               Table of Contents for the Online Textbook