5.3 Natural Law Theory

Happiness is secured through virtue; it is a good attained by man’s own will.

—St. Thomas Aquinas

Natural Law Theory (NLT), as the name suggests, argues that there are standards for right and wrong and these are to be found in nature. Natural things are built (whether by a divine creator or by Darwinian evolution doesn’t matter here) to be good at certain types of things. Fish are good swimmers, but bad typists. Dogs are good at smelling things in your luggage, but bad at flying. Trees are good at turning solar energy, water and carbon dioxide into sugars, and bad at solving calculus problems. Another way of saying the same thing is to appeal to the concept of a natural function: fish, dogs, trees, and all other natural things, including us humans, have a certain set of built in potentials, or functions, things they are built to do and can do well. Things that are not part of their natural abilities they shouldn’t be doing at all. Natural law theory in ethics is based on this idea. Human beings have a certain set of things we can all do and that we can also do well or poorly. By nature us humans can:

  • move physically through our surroundings;
  • perceive things around us and learn about how the world works through observation and experiment;
  • maintain our bodies and minds in a healthy state;
  • be emotionally engaged in our lives and the lives of others;
  • be creative and enjoy the products of others’ creativity;
  • be productive and politically active members of society;
  • have and raise children.

All of these capacities combined make up what humans can do by nature. In spite of the fact that this list seems long, there are of course plenty of things that we cannot do by nature, like fly under our own power, or survive underwater without an artificial air supply. Given all of this, the fundamental claim of Natural Law Theory is just that ethics can and should be based on these natural functions. Ethical decisions are decisions that follow from and foster human nature, while unethical decisions are those that go against our natures. So far this may not seem to be a particularly religious approach to ethics as it was billed above. In a sense, the religious reading of natural law theory is optional – the claims it makes could be cast in an entirely secular light, by simply referring to nature. However, not only is the most popular version of this theory the one embraced by the Catholic Church, but the tradition from which this theory arose saw nature as the result of supernatural forces at work – God’s creation. So even the religious aspect of Natural Law Theory may not be required for the theory itself, to the extent that talk about natural purposes evokes the purposes of the creator of natural things, the two are closely connected.

According to NLT

  • Understanding things requires understanding their purpose.
  • Human nature is clearly visible by the “light of reason.”
  • It is better to follow the natural order of things than to oppose it.

Implications of NLT

This theory may sound simple and even a little trivial, but, as we shall soon see, it has far-reaching implications. In addition, it fits in very well with certain intuitions we may have about what is involved in living a good life. We all have some conception of what a good life would look like, and our individual conceptions of a good life no doubt overlap. Among others, elements of a good life would include:

  • having a healthy body and mind;
  • knowing enough about our world to be able to effectively realize our personal goals;
  • having friends and a family who love and understand us, and who are willing to help us out in times of need;
  • living in a comfortable community with people who share our values;
  • having an interesting and rewarding job that fits our abilities.

According to NLT it is no accident that these are elements of a good life in most peoples’ view, because all of these things involve realizing or fulfilling some of our naturally given capacities mentioned above. In fact, for NLT, living a good life is not only what many people aspire to, it is the naturally given goal of human beings. Fulfilling our natural capacities, realizing the set of capacities we are all born with is also what we should strive for. We should, to borrow a famous slogan, “Be all we can be.” In the eyes of a backer of NLT this slogan is not intended only as a way of encouraging us to do our best, it is also an expression of an ethical demand – we should strive to realize our natural potential to the greatest extent possible and we are acting wrongly if we do not listen to this demand.

But what about people who fail to realize their naturally given potential? In some cases people are prevented from realizing their potential because of factors outside of their control, such as disease or accidents. Someone afflicted with a childhood disease may be prevented from ever realizing the potentials they were born with and this is an unfortunate accident. But someone who has no excuse besides, say laziness, who fails to live up to his or her potential deserves to be condemned. Such a person is a “slacker,” a “dead-beat,” living a wasted life – even the language we use to describe someone who fails to live up to their potential has a tone of moral disapproval. For a backer of natural law theory, a person who does not follow human nature and strive to be all that they can be is wrong to do so.

On the other hand, if a whole society is filled with people who fail to realize their potentials, this is good grounds for suspecting that there is something wrong with the way in which that society is run. In fact, both nations and international organizations such as the United Nations increasingly measure the prosperity of countries not just by GDP growth rates, but by determining to what extent people are well-fed, employed, educated, in good health, etc. It is a common assumption (is it warranted?) in international affairs that if a country is systematically preventing its citizens from realizing their potential, if it is frustrating the fulfillment of their basic human needs, then there is something wrong with that society and it should be encouraged or prodded to change.

Taking this idea still further, in the hands of Aquinas, Natural Law Theory leads to the idea that there are certain absolute values, things that we must value without exception. If human flourishing is an ethical demand that nature makes on us by providing us with a set of built-in capacities, there are certain things that we must always value as preconditions for realizing those capacities. These are, in Aquinas’ view,

  • life
  • procreation
  • knowledge
  • sociability

If we fail to honor these values, we cannot realize our potentials as nature (or its creator) intends. This is most obvious for the first of these absolute values, but the case could be made that if we fail to have children, seek knowledge and develop our social abilities, us human beings would fail miserably in our attempts to realize our natural capacities. It is for this reason that these values simply must be honored – everything else depends on them. Such are the implications of the theory – now on to the important question, “But is it true that right and wrong can be determined by how well or poorly we live up to our natural potentials?”