Natural Law Revision

There are a number of features of natural law theory:

The theory of Natural Law was put forward by Aristotle but championed by Thomas Aquinas (1225-74). Natural Law has elements of both of these approaches. Man desires happiness, but for Aquinas this means fulfilling our purpose as humans. He said, in Summa Theologica, “whatever man desires, he desires it under the aspect of good.” Fulfilling our purpose is the only ‘good’ for humans.

  • Deontological because it produces rules and duties Strictly speaking, it’s a deontological theory which comes out of a teleological worldview, the Greek view that everything has a purpose (telos) and the purpose of human beings is distinctive and rational.
  • Absolutist because the natural law is absolute and unchanging, “a sharing
    in the eternal law by intelligent creatures” (Aquinas). However, it is only the primary precepts of the natural law that are unchanging as will be explained (not secondary precepts).
  • Normative because natural law creates norms or values which are inherent in the natural order, accessed by our reason.

Natural Law assumes that human beings, made in the image of God, by their very nature desire to do good and avoid evil and so all human beings (believer or unbeliever) when fulfilling their rational purpose, pursue good ends. Wrong actions therefore break the law, and law to Aquinas has four meanings:

  • Eternal Law is God’s plan for creation.
  • Divine Law is revealed in the Bible, and alters between the Old and NewTestaments.
  • Natural Law is discoverable by the use of right reason, observing natural endsand purposes. It includes primary and secondary precepts.
  • Human Law is passed by governments (Aquinas uses the word “promulgated”) and corresponds to the natural law, so that “a human law diverging in any way from the natural law will be a perversion of law and no longer a law”

Five Primary Precepts

Aquinas stated that there were certain fundamental laws set by God and that humans should follow these laws and apply them to decision making throughout life. These laws are:

  1. self preservation 
  2. continuation of the species through reproduction 
  3. education of children
  4. to live in society
  5. to worship God

He called these the Five Primary Precepts, and from these developed secondary precepts which are to help people live by the five primary ones.

Secondary Precepts

Humans are then to use their reason to establish rules that will fulfil the requirements of the primary precepts. These rules are known as secondary precepts.

Some examples are:

  • Do not murder (fulfils the primary precept of preserving the innocent)
  • Do not abort the unborn (fulfils the primary precepts of preserving the innocent and of continuing the species)


At times humans use their reason incorrectly because they are following apparent goods rather than real goods.

Task: Give an example of a real and apparent good.

Aquinas also noted that God knows the secrets of our hearts and so our actions must be interior rather than exterior – the motive behind an action counts.

Task: Give examples of interior and exterior actions.

Natural Law theory might appear on first glance to be inflexible – but before we pass over hasty judgement we need to consider the doctrine of double effect. Thomas Aquinas introduced this principle when considering killing in self-defence. Killing an attacker is justified, he argues, as long as I do not intend to kill them. Augustine had argued (in contrast) that killing in self-defence was not moral, arguing that “private self-defence can only proceed from excessive self-love.” Notice how this makes Natural Law theory a lot more flexible than sometimes described, adding an element of intention and of proportionality to the moral decision. Aquinas observes that “nothing stops an act from having two effects, only one of which is intended, while the other is unintended. … so the act of self-defence may have two effects: one, saving my life; the other, killing an attacker.”

In recent decades there has been a move to simplify natural moral law and to make it more applicable to everyday life. Proportionalists such as Bernard Hoose have suggested that natural moral law is not just lists of absolute “thou shalt not”s but a system of guidelines which individuals must navigate for themselves.

For example, we know that disobeying a parent is wrong, it generally goes against the primary precept of pedagogy, however in some circumstances it may be right to disobey the order ‘don’t run inside’, such as when there has been an accident and an ambulance is needed. It may sometimes be right to do a wrong thing.


Task: Read the handout on Natural Law. Create a summary map.

Advantages of Natural Law

  • There is a fair set of rules for everyone.
  • However, it is not just a large number of rules dictating what we should do.
  • All the things that are good for us are celebrated, rather than focusing on negative things.
  • Humans are at the centre of this ethical approach, not rules.
  • It allows us to use our reason and so feel in control of the secondary precepts.
  • It allows people to establish common rules in order to structure communities.

Disadvantages of Natural Law

  • In modern forms Natural Law does not allow for negotiation because the Church has made the secondary preceptsinto absolute rules.
  • It is based on very complicated notions and doesn’t ask everyday questions such as ‘should hospitals get more money than schools’?
  • It could be argued that we have gained our natural instincts through evolution, not through God and so we do not need a God-based theory.
  • We can observe differences between cultures, which rejects the notion of a single natural purpose for all humans.
  • Natural Law could even be seen as a relativist theory – because the secondary precepts might change as we use our reason differently, perhaps because of the different circumstances we find ourselves in. This could be seen as an advantage or a disadvantage! Indeed, some say that we should not rely on our reason but on teachings from the Bible, the Church or from God’s revelation.
  • Vardy and Grosch in The Puzzle of Ethics said that Aquinas gives too simple a view of human nature. (E.g. is sexuality just about reproduction?)
  1. “Natural Law does not present a helpful method for making moral decisions”. Discuss
  2. “Moral decisions should be based on duty, not purpose”. Assess with reference to the theory of Natural Law.
  3. “Human beings are born with the tendency to pursue morally good ends”. Evaluate in the light of teleological aspects of Natural Law.
  4. “Explain and justify the doctrine of double effect with reference to an ethical dilemma of your choice concerning euthanasia”.
  5. Critically assess the view that natural law is the best approach to issues surrounding sexual ethics

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