Natural Law


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Telos & the four tiers of law

Aquinas developed Natural law as a form of religious ethics. Natural law is the theory that God has designed a moral law into human nature such that we are naturally inclined to certain moral behaviours. Ethics is therefore about using reason to discover the natural law within our nature so that we can conform our actions to it in order to fulfil our purpose (telos) of glorifying God, by following his law.

“the light of reason is placed by nature in every man, to guide him in his acts towards his end”. – Aquinas.

The four tiers of Law. The ultimate source of moral goodness and thus law is God’s nature, which is the eternal law. However, that is beyond our understanding, so we have access to lesser laws that derive from the eternal law.

Eternal Law – God’s omnibenevolent nature.
Divine law – God’s revelation to humans in the Bible.
Natural law – The moral law God created in human nature, discoverable by human reason.
Human law – The laws humans make which should be based on the natural and divine law.

The purpose of the four tiers is to show how Aquinas thinks that human law can gain its authority by deriving from the natural and divine law which themselves ultimately derive authority from God’s nature.

Aquinas was influenced by Aristotle’s views that there is a natural end to things – everything has a purpose (telos) built into it by its nature – the final cause. Whereas Aristotle thought the final cause of all things was the prime mover, Aquinas Christianised the concept and claimed that it was God. The telos/end/goal of rational beings is the good, which is God’s eternal law. God created us and our nature to have the telos of glorifying God. We can use our God given reason to figure out the inclinations of our God-designed nature. That will then tell us how we should live, i.e. ethics.

The Primary Precepts & Synderesis

Aquinas claims that reason is a power of the human soul and synderesis is the habit or ability of reason to discover foundational ‘first principles’ of God’s natural moral law which gives us insight into God’s intentions for human life and thus our telos.

“the first practical principles … [belong to] a special natural habit … which we call “synderesis” … is said to incite to good, and to murmur at evil, inasmuch as through first principles we proceed to discover, and judge of what we have discovered.” – Aquinas.

The first principle synderesis tells us is called the synderesis rule: that the good is what all things seek as their end/goal (telos). This means that human nature has an innate orientation to the good.

“This therefore is the principle of law: that good must be done and evil avoided.– Aquinas.

In addition to this, synderesis tells us the primary precepts: worship God, live in an orderly society, reproduce, educate, protect and preserve human life and defend the innocent. These primary precepts are the articulation of the orientations in our nature toward the good; the natural inclinations of our God-designed human nature, put into the form of ethical principles by human reason.

Secondary precepts & conscientia

“there belongs to the natural law, first, certain most general precepts, that are known to all; and secondly, certain secondary and more detailed precepts, which are, as it were, conclusions following closely from first principles.” 

The primary precepts are applied to situations or types of actions – a process called conscientia. The judgement we then acquire is a secondary precept. E.g euthanasia: the primary precepts don’t say anything about euthanasia exactly, but we can use our reason to apply the primary precepts to euthanasia, and realise that it goes against the primary precept of protecting and preserving human life. Arguably it even disrupts the functioning of society too. Therefore, we can conclude the secondary precept that euthanasia is wrong.

Interior & exterior acts

Aquinas draws a distinction between the action itself, which is an exterior act because it occurs outside of our mind, and our intention which is the interior act because it occurs inside our mind.

The point of natural law ethics is for us to figure out what fulfils the telos of our human nature and then act on it. By doing so, we glorify God. This cannot be done without intending to do it.

A good exterior act without a good interior act does not glorify God because it is not done with the intention of fulfilling the God-given goal/telos of our nature.

The act of giving money to charity is an example of a good exterior act, but is only morally good when combined with the right kind of intention, which would be an interior act. If the intention was only to be thought of as a good person, which is not the right kind of intention, then the action was not truly morally good.

Real vs apparent goods

Aquinas’ natural law ethics relies on human reason to understand and apply the natural law. Yet, human reason is fallible. It is unavoidable that sometimes our reasoning about what is morally right will err.

We might reason that something is in accord with our nature’s goal and is thus good, when really is not. A common cause of our reasoning being faulty is that we can be misled by the temptation of short-term pleasures into being blind to an actions’ long-term negative consequences for achieving our telos. For example, adultery might seem like a good idea at first if one is focused only on the short-term pleasure, yet the consequences for raising children which is our real goal might be put at risk. Such actions are called apparent goods because they only appear good to someone engaged in faulty reasoning. They are not real goods.

The double effect

Aquinas argued that a single action can have two effects, one in accordance with the primary precepts and one in violation of them. Being a good person involves developing the kind of virtuous character which acts with the intention of following God’s natural law. Aquinas first introduced this as a way to justify killing in self-defence. Aquinas insists there are two effects; the saving of a life and the killing of a life. He claims that in such cases it can be that one effect is intended while the other effect is “beside the intention”. So, Aquinas thinks killing someone, which clearly violates the primary precept of preserving human life, can be justified so long as it is an effect which is a secondary effect beside the intention of an action whose other effect was intended and was in accordance with the primary precepts.

There are four generally accepted conditions in modern catholicism for an action to be justified by the double effect:

The intentionality condition. The good effect must be intended and the bad effect must be ‘besides the intention’.

Aquinas illustrated the double effect with the example of killing someone in self-defence. So long as you intended to save your own life, then it is morally permissible to kill someone in self-defence. The bad effect is ‘besides the intention’. 

The proportionality condition. The good effect must be at least equivalent to the bad effect. Saving your life is equivalent to ending the life of the attacker. You can’t use more force than is necessary to save your life – there must be proportionality there too. 

The means-end condition. The bad effect and the good effect must both be brought about immediately – at the same time. Otherwise, the person would be using a bad effect as a means to bring about a good effect – which is not permissible.

The double effect only applies to actions which have two effects – one good, one bad – where both effects are brought about immediately.

The nature of the act. The action must be either morally good, indifferent or neutral. Acts such as lying or killing an innocent person can never be justifiable. An attacker would not count as an innocent person.

Whether Aquinas is too optimistic about human nature

Strength: Aquinas has a realistic view of human nature, that while it contains the bad of original sin, it also contains an orientation (telos) towards the good (eudaimonia) and it is up to us to choose rightly.

Weakness: Aquinas is too optimistic about human nature. If you consider the terrible things that humans have done and that entire cultures have embraced, e.g. slavery and Nazism, it starts to look like human nature is not as positive as Aquinas thought. If we really had an orientation towards the good and the primary precepts accurately described our nature’s orientation, then we should not expect to find the extent of human evil we do.

Evaluation: However, Aquinas’ claim is merely that human nature contains an orientation towards the good, it doesn’t involve a commitment to humans actually doing more good than evil, nor to incredibly evil acts or cultures occurring infrequently. Aquinas acknowledges that there are many reasons we might fail to do good despite having an orientation towards it. These include original sin, mistakes in conscientia, lacking virtue and a corrupt culture.

Evaluation: The fact that humanity could sink so low as to produce Nazism and the holocaust is strong evidence against the human nature having an orientation toward the good.

Aquinas vs modern science on the issue of telos/purpose

Strength: Natural law recognizes that we have a purpose (telos).

Weakness: Modern science’s rejection of final causation. Francis Bacon, called the father of empiricism, argued that formal and final causation (telos) have no place in empirical science but are instead matters for metaphysics. He thought purpose was a divine matter. Regarding form, he gave the illustration of the ‘whiteness’ of snow and explained how science could investigate how snow results from air and water, but this only tells us about its efficient cause, not the form of ‘whiteness’, which is thus not a scientific matter.

Modern physics goes even further than Bacon in its rejection of final causation. A deterministic universe operating by the laws of physics seems to be completely without purpose. All supposed telos of an object can be reduced to non-teleological concepts regarding the material structure of an object. This suggests there is no basis for grounding telos in God like Aquinas did, or in grounding it as a required explanation of change in objects like Aristotle did. Modern science can explain the change and apparent purpose in the world without telos.

Evaluation: Science cannot rule out something like a prime mover or God which could provide some kind of external telos, however.

Evaluation: Nonetheless, at the very least the current scientific understanding of the universe works without the need for any kind of telos. A century after Bacon, Laplace wrote a book on the workings of the universe, claiming to have ‘no need’ of the hypothesis that there is a God. More recently, Stephen Hawking made the same claim.

Fletcher’s critique of Natural law ethics

Strength: Natural law is based on human nature. The primary precepts are found in the morality of all societies, which shows that we are all born with a moral orientation towards the good.

Weakness: Fletcher’s critique. If all humans were really born with the ability to know the primary precepts, we should expect to find more moral agreement. In fact, we find vastly different moral beliefs. Not only that, differences in moral views tend to fall along cultural boundaries. This suggests that it is actually culture and upbringing which causes our moral views, not the natural law. Freud claimed that it is society which conditions our moral views. Fletcher explicitly targets Aquinas with these points, claiming that this shows there is not an innate God-given ability of reason to discover a natural law. The primary precepts that Aquinas thought were human nature was really just his culture.

Evaluation: However, there do seem to be some core similarities between the moralities of different cultures such as not killing for no reason and rules about stealing. Reproduction and education are also universal. Moral thinkers from different cultures came up with similar moral prescriptions such as the golden rule; to treat others as you would like to be treated, which can be found in ancient Chinese Philosophy, Hinduism, Judaism and Christianity. This could be taken to show that moral views are determined by a universal human moral nature.

Evaluation: Alternative explanation: cross-cultural morality might result merely from the basic requirement of a society to function. If anyone could kill or steal from anyone else for no reason whenever they wanted, it’s hard to see how a society could exist. That might create an existential pressure which influences the moral thinkers of a society, yielding prescriptions such as the golden rule. Cross-cultural ethics therefore has a practical reality as its basis, not God.

Furthermore, cross-cultural similarities in moral codes might also have resulted from a biologically evolved morality rather than one designed by a God, which would mean it is not related to a telos designed by God.

Aquinas’ Natural theology vs Karl Barth’s protestant critique

Strength: A strength of natural law is its use of reason, such as in applying the primary precepts. Aquinas’ natural theology. Aquinas accepted that human reason could never know or understand God’s infinite divine nature. However, he argued that human reason can gain lesser knowledge of God, including God’s moral law through natural law theory. This makes Aquinas a proponent of natural theology through reason, which he claimed could support faith in God.

Weakness: Augustine & Karl Barth on Original Sin vs Aquinas’ Natural Theology

Karl Barth was influenced by Augustine, who claimed that after the Fall our ability to reason become corrupted by original sin. This is a problem for natural theology which wants to make use of reason.

Barth’s argument is that is therefore dangerous to rely on human reason to know anything of God, including God’s morality. He said “the finite has no capacity for the infinite”, meaning our finite minds cannot grasp God’s infinite being. Whatever humans discover through reason is not divine, so to think it is divine is idolatry – putting earthly things on the level of God. Idolatry can lead to worship of nations and even to movements like the Nazis. After the corruption of the fall, human reason cannot reach God or God’s morality. Only faith in God’s revelation in the bible works.

Aquinas accepts that God’s infinite nature is beyond our understanding. He is trying to claim that reason can understand the natural law God created within our nature and that some necessary being or uncaused cause exists. Nonetheless, Barth claims that reason has ‘no capacity’, i.e., zero ability, to know anything whatsoever of God. It is corrupted by original sin and therefore Aquinas’ natural theology is dangerous for relying on it.

Evaluation: Aquinas defends his natural theology from original sin. Aquinas claims that pre-fall human nature contained three ‘goods’:

  1. the properties of a human soul, e.g. rationality.
  2. An inclination towards the good (telos) as a result of being rational.
  3. Original justice/righteousness; perfect rational control over the soul.

Original sin completely destroyed original justice, which caused us to lose perfect rational control over our desires. Nonetheless, Aquinas argues that our rationality and its accompanying inclination towards the good was not destroyed by original sin.

Aquinas argues that only rational beings can sin. It makes no sense to say animals sin, for example. The doctrine of original sin claims that post-lapsarian humans are sinners, so, we can sin. It follows that we must still be rational beings to some degree. Our reason therefore still inclines us, through synderesis, towards goodness.

Furthermore, Aquinas diverges from Augustine, claiming that concupiscence can sometimes be natural to humans, in those cases where our passions are governed by our reason.

Aquinas concludes that original sin has not destroyed our orientation towards the good nor is our reason always corrupted. Original sin can at most diminish our inclination towards goodness by creating a habit of acting against it. Sometimes, with God’s grace, our reason can discover knowledge of God’s existence and natural moral law. So, natural theology is valid.

“Participation of the eternal law in the rational creature is called the natural law”. – Aquinas

Arguably Aquinas has a balanced and realistic view, that our nature contains both good and bad and it is up to us to choose rightly.

Counter-evaluation: However, Barth still seems correct that being corrupted by original sin makes our reasoning about God’s existence and morality also corrupted. Even if there is a natural law, we are unable to discover it reliably. The bad in our nature unfortunately means we cannot rely on the good. Whatever a weak and misled conscience discovers is too unreliable.

Humanity’s belief that it has the ability to know anything of God is the same arrogance that led Adam and Eve to disobey God. Humanity believing that it has the power to figure out right and wrong is what led to the arrogant certainty of the Nazis in their own superiority. This arrogance of natural theology is evidence of a human inability to be humble enough to solely rely on faith.

Whether Natural law ethics is outdated

Strength: Natural law ethics is available to everyone because all humans are born with the ability to know and apply the primary precepts. It is possible to follow the natural law even if you are not Christian or have no access to the divine law (Bible).

Weakness: Aquinas’ Natural law ethics is increasingly seen as outdated. In ancient and medieval history, society was more chaotic. It made sense to create strict absolutist ethical principles, to prevent society from falling apart. This would explain the primary precepts. They served a useful function in medieval society.

It was useful to restrict sexual behaviour to marriage, because of how economically fatal single motherhood used to be. It was useful to simply ban all killing, because killing was much more common and needed to be strongly restricted. It was useful to require having lots of children, because most children died.

The issue clearly is that all of these socio-economic conditions have changed. So, the primary precepts are no longer useful. They were designed for a different time and are now increasingly outdated. Society can now afford to gradually relax the inflexibility of its rules and think about how they might be reinterpreted to better fit modern society.

Evaluation: Aquinas could be defended that this doesn’t actually make his theory wrong. Perhaps our society has simply gone the way of the devil! The fact that mainstream culture has moved on from natural law ethics doesn’t mean it were right to. If Hitler had won WW2 and enslaved humanity, then democracy might have been viewed as ‘outdated’, but that wouldn’t make it wrong. Calling an ethical theory outdated is not a valid argument.

Counter-evaluation: A better version of the ‘outdated’ critique is to argue that Aquinas’ theory was actually a reaction to his socio-economic context and since that has changed, Natural law is no longer relevant.

Aquinas thought that he discovered the primary precepts through human reason, as God designed. However, arguably it’s a simpler explanation that Aquinas was simply figuring out what would have been good for people in his socio-economic condition. That the resulting principles actually came from God was only in his imagination.

Whether the double effect is unbiblical

Strength: Natural law has flexibility due to the doctrine of the double effect.

Weakness: the double effect is unbiblical. Some theologians reject the double effect as unbiblical because God’s commandments are presented as absolute and not dependent on someone’s intention. For those theologians, the distinction between intended effects of actions and merely foreseen effects “beside” the intention has no morally relevant significance. It’s not that intention has no relevance in traditional Christian ethics. Most theologians accept that people are not immoral for consequences of their actions which they could not have foreseen which violate God’s commands. For example if you decide to drive your car at the time a drunk person happened to be out and you ran them over, that would not be considered your fault even through it was an effect of your action. However if you could foresee a bad consequence, the fact that it was a secondary effect beside the effect you did intend doesn’t justify it for theologians who take this view.

Evaluation: Natural law is different to the Bible though. The Bible might be inflexible, but that is the divine law. The natural law in our nature is more flexible because it is in the form of very general precepts which require application and the telos of the natural law is glorifying God, which requires that it be our intention to glorify God – thus showing how intention is relevant.

Whether the double effect makes Natural law flexible enough

Weakness: Self-sacrifice example. Arguably the double effect does not accurately capture why we find certain rule-breaking acceptable. Consider the example of a soldier throwing himself on a grenade to save his fellow soldiers. This seems to be a heroic act however it’s hard for the double effect to make sense of it, because the double effect would require the bad effect of suicide to be foreseen but besides the intention of the heroic soldier. However, that seems inaccurate because it is part of the heroism of the act that the soldier intends to sacrifice their own life. Natural law, as can be seen by the secondary precepts and the double effect, is trying to introduce flexibility into Christian ethics, but arguably it fails to introduce enough flexibility as this case shows. This prompts some to go further and accept proportionalism or even situation ethics.

Evaluation: defence of Aquinas. However, arguably Aquinas could accept that soldier’s actions were heroic. If we think carefully about the way Aquinas explains the double effect. He says the bad effect must be ‘beside’ or ‘outside’ the intention. The soldier didn’t ultimately want to die, they wanted to save their fellow soldiers. Dying was the means of saving them and so dying had to be intended. However arguably it is still nonetheless beside the intention. The soldier’s death was not unintended but it was beside their intention.

Possible exam questions for Natural law 

Does natural law provide a helpful method of moral decision-making?
Assess Aquinas’s natural law ethics.

Can judging something as right or wrong be based on whether it achieves its telos?
Does human nature have an orientation towards the good?
‘Ethics can be derived from human nature’ – How far do you agree?
Assess Aquinas’ claim that there is a tier of natural law between human and divine.
How ethical are the primary precepts?
Is there a moral law of God within human nature that is discoverable by reason?”
Evaluate Aquinas’ view that human law should be related to the natural law.

Is the universe designed with a telos?
How ethically valid is the doctrine of the double effect?
Does the doctrine of the double effect justify actions like killing in self-defence?
If human nature is sinful, can natural law theory work?
Analyse Aquinas’ four tiers of law.
“The eternal, divine and human laws are the only valid laws” – Discuss.
Critically assess Aquinas’ religious development of Aristotle’s concept of telos.

Quick links

Year 12 ethics topics:
Natural Law.
Situation ethics. Kantian ethics. Utilitarianism.
Euthanasia. Business ethics. 

Year 13 ethics topics:
Conscience. Sexual ethics. 

OCR Philosophy
OCR Christianity
OCR essay structure
OCR list of possible exam questions