Natural Law Ethics 

An early attempt at answering the "Why be Moral?" challenge to Divine Command Ethics, is the Natural Law theory of ethics described by Thomas Aquinas.(1)  He theorized that the world is governed by natural laws (divinely given, of course).  And that Man can discover these natural laws, and govern his life according to them.  Effectively, Aquinas has chosen the second horn of the Euthyro Dilemma.

Aquinas argued that when we focus on man's role as recipient of the natural law, the natural law constitutes the principles of practical rationality.  It is against the dictates of the natural law that human action is to be judged as reasonable or unreasonable.  Natural law is the preeminent part of the theory of practical rationality.(2)  Thomas Hobbes can also be classified as a natural law theorist.(3)  Like Aquinas, Hobbes held that the laws of nature are divine law, that all humans are bound by them, and that it is easy to know at least the basics of the natural law.  Of course, if one maintains the premise that these Natural Laws have God as the law giver, then there is little difference between Natural Law Ethics and Divine Command Ethics.  All of the flaws infecting Divine Command Ethics will also infect Divine Natural Law Ethics.

But there are a number of Ethical theorists who deny this premise, and offer Naturalistic Moral Law theories.  For example, there are the theories of Michael Moore(4) , Philippa Foot(5) , John Finnis(6) ,  Alasdair MacIntyre(7)  and Mark Murphy(8).  Naturalistic moral law theories maintain that there is a natural order to our world that should be followed.  It is an absolute theory of ethics that is not routed in duty or in externally imposed rules, but in our human nature and our search for genuine happiness and fulfillment.  Like Hobbes (Leviathan, xiv, Sect 3), they all argue that the fundamental good is self-preservation, and that the laws of nature direct the way to this good.  These theorists use reason to discover the laws governing human nature and natural events, and apply these laws to thinking about human action.  Within these theories, actions in conformity and support of natural laws are morally correct.  What is consistent with the Natural Law is Right, and what is not in keeping with the Natural Law is Wrong.  For example, it is argued that Humans have a natural drive to eat, drink, sleep and procreate.  These actions are in accord with the natural laws for species to survive and procreate.  Thus activities in conformity with such laws are morally good.  Activities that work against these laws are morally wrong.  As an example consider that to eat too much or too little and place your life in jeopardy is morally wrong.  This reasoning appears to place Natural Law Ethics firmly on the Personal Ethics side of the divide.  (But see below for a demurrer.)

In answer to the challenge of "Why be moral?" then, Naturalistic Moral Law theorists provide the answer "To achieve genuine happiness and fulfillment".  Unfortunately, this sort of answer makes the ethical theory in question more of a consequentialist theory than a deontological one.  Within deontology, one obeys the rules because they are the rules.  One does one's duty because it is one's duty.  But this deontological approach, as I outlined earlier, leaves the question of "Why be moral?" open.

Also there remain two main flaws to Naturalistic Law Ethical theories.  The first, was advanced by David Hume.  He argued that Natural Law theories conflate that which is the case with that which ought to be the case.  There may be, as these theories maintain, a natural order to the world.  But that does not logically imply that we ought to follow it.  One cannot, as Hume pointed out, logically derive a moral imperative or value judgment simply by observing the facts of nature.  It may be a fact of nature that we need so many calories on a daily basis to keep on living.  But that offers no prescription about how many calories we ought to consume.  Not unless you include the prior moral premise that we ought to keep on living.  But there are no natural facts of the matter, and no law of nature, that suggests this need be the case.

The second flaw is an extension of the first.  Naturalistic Moral Law Theories assume that moral principles are written in the laws of nature.  Modern science is generally understood to contradict this assumption.  The scientific perspective sees only cause and effect in the natural world.  Science, it is often claimed, does not see moral principles and values.  These have to be provided by extra-scientific assumption.  Science can point the way to genuine happiness, only if that concept is defined in terms of individual subjective evaluation of what makes us happy.  And that leads to a subjectivist ethic, rather than an absolute ethic.  Similarly, the notion of fulfillment is either going to be a matter of subjective personal opinion, or is going to beg the initial question.

The third (and more trivial) problem facing Natural Law Ethics, is the difficulty in placing such theories on the Social versus Personal conceptual divide.  On the one hand, Natural Law Theorists answer the "Why be Moral?" challenge by claiming that the life of the individual moral agent will be happier and more fullfilled if the agent follows the rules dictated by the Natural Laws.  But on the other hand, these Laws ought to be obeyed even to the detriment of the individual moral agent.  In other words, even if it appears that following the Natural Law in some particular circumstance might not be in the interests of the moral agent, really it actually is.  (Hmmm?  And the evidence for this is?)

As a result of these flaws, Natural Law Ethics plays virtually no role in contemporary secular moral discourse.(9)  Or perhaps more accurately, the role once assumed by Natural Law Ethics has been incorporated into other Consequentialist Ethical theories. 

Deep Genesis Challenge

Which still leaves us with the challenge of explaining why happiness and personal fullfillment matter, and why these particular rules and goals should happen to lead to happiness and personal fullfillment.  If moral principles are in fact written in the laws of nature, why should these particular principles lead to our happiness and fullfillment rather than those principles?  Accepting the situation as a fait acompli, closed to further investigation, renders morality a matter of differing opinions on the interpretation of the Moral Laws.

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(1)  Aquinas, Thomas;  Summa Theologiae (Complete and Unabridged), translated by the Fathers of the English Dominican Province, Coyote Canyon Press, 1274/2010, Kindle Edition, ISBN 1-480-03169-0.

(2)  Murphy, Mark; "The Natural Law Tradition in Ethics" in The Stanford Encyclopedia of Philosophy, Edward N. Zalta (ed.), URL=<>.

(3)  Hobbes, Thomas;  Leviathan: Revised Student Edition (Cambridge Texts in the History of Political Thought), Richard Tuck, Ed., Cambridge University Press, Cambridge, England. 1651/1991. ISBN 978-- 0-521-- 56797-8. Kindle Edition.

(4)  Moore, Michael;  "Good without God," in Robert P. George (ed.) Natural Law, Liberalism, and Morality, Oxford University Press, Oxford, England. 1996.

(5)  Foot, Philippa;  Natural Goodness, Oxford University Press, Oxford, England. 2001.

(6)  Finnis, John;  Natural Law and Natural Rights, Oxford University Press, Oxford, England. 1980.

(7)  MacIntyre, Alasdair;  After Virtue, University of Notre Dame Press, Notre Dame, Indiana. 1991/2008. ISBN 978-0-26803504-4.

(8)  Murphy, Mark C.;  Natural Law and Practical Rationality, Cambridge University Press, New York, New York. 2001.

(9)  Rachels, James;  The Elements of Moral Philosophy. The McGraw-Hill Companies, New York, New York. 2007. ISBN:  978-0-078-03824-2. Pg 60.