Aquinas was born into a life of some privilege in about 1225. His father was a count living at the castle of Roccasecca at Aquino, between Naples and Rome. After school and university Aquinas defied his father by becoming a Dominican monk (a Catholic order still celebrated for its learning and teaching). Among his many writings, two massive works are particularly significant: first the Summa Contra Gentiles (āa treatise against heathensā) and then, towards the end of his life, the Summa Theologica (āa theological treatiseā). His highly influential understanding of natural law can be found in both of these works, although the first is more apologetic in intent than the second.
At the time, these two works were considered dangerous innovations, particularly because they made great use of the Greek philosopher Aristotle rather than the more widely accepted Plato. In both of his works Aquinas was concerned to show that the Christian faith rests upon a rational foundation. Aristotleās work, preserved in the Islamic world, provided him with the intellectual framework for this and avoided some of the theological speculations of Plato. Aquinas believed that Aristotleās naturalistic framework could indeed work harmoniously with Christian revelation.
Shortly before his death in 1274 he had a number of mystical experiences, including one while saying Mass ā after which he stopped work on his Summa Theologica, saying that āall I have written seems to me like so much straw compared with what I have seen and with what has been revealed to meā. He died in France on his way to a papal conference in Rome.
Natural law in the Summa Theologica
Summa Theologica asks a series of questions about natural law, including:
- Whether all acts of virtue are prescribed by natural law?
- Whether natural law is the same for everyone?
- Whether natural law can be changed?
- Whether natural law can be abolished from the human heart?
Whether all acts of virtue are prescribed by natural law?
Aquinas follows Aristotle in making a connection between natural law and virtue. Everything is inclined by natural law to a mode of operation that is suitable to its own form. For example, fire is inclined to give heat. Human beings, uniquely possessing a rational soul, are inclined by natural law to act according to (some) virtues and thus to promote their own well-being.
Whether natural law is the same for everyone?
Aquinas follows Aristotle again in accepting that all human beings have some awareness of natural law and thus possess a natural tendency or inclination towards virtue and well-being. Primary principles about what is right or wrong can be known through the use of reason alone. Of course, human rationality can be distorted ā human beings are fallible ā but the theoretical principles of natural law are the same for everyone everywhere.
For example, Aquinas notes, theft is always wrong and against natural law, even though some in the ancient world did not recognise that it is so. He insists that we are all capable through reason of discovering that theft is wrong as a general principle. However, in particular cases restoring goods held in trust might be unreasonable if they were intended for use to fight against oneās own country. In this context a failure to restore goods would not be theft.
So it is natural for human beings to act according to reason and, from their use of reason, to discern what is good and what is bad. Truth about primary or general principles is the same for everyone, whether everyone recognises this or not. Secondary principles, derived from the general principles and concerned with detailed action in changeable contexts, are also the same for most people. However, error, sin or bad customs may distort these secondary principles.
Whether natural law can be changed?
Aquinas makes a distinction here between change by addition and change by subtraction. He sees little problem with change by addition, noting that human and divine laws (which cannot be discerned solely through reason) may be added to natural law (which can be so discerned). Although humans cannot contradict natural law, they can sometimes add to it. God can indeed add to it.
Subtraction, however, is quite a different matter. Here, general or primary principles are unalterable and cannot be subtracted. Yet secondary principles may occasionally be changed by subtraction. To take the example of theft again; Aquinas argues that, since all things finally belong to God, taking something from another person on Godās command would not be theft. More contentiously, he also argues that adultery ā understood as sexual intercourse with another personās spouse ā is always against reason and wrong, but, if such an act were to be commanded by God, it would not be wrong and it would not be adultery
Whether natural law can be abolished from the human heart?
Aquinas insists that general or primary principles cannot be blotted out or abolished from the human heart. They are known, at least in the abstract, to all people. Human nature endures despite human sinfulness.
However, in practice, secondary principles, relying upon primary principles, can be blotted out or abolished by evil opinions, speculative errors, bad customs or corrupt habits.
Natural law beyond the Summa Theologica
In the chapters that follow, one more section of the Summa Theologica on natural law will be summarised (in Chapter 3 on war and peace). However, in Chapter 4 (on the environment) and in Chapter 6 (on sexuality) the sections will be summarised from the Summa Contra Gentiles. The latter demonstrate with particular clarity how Aquinas deployed natural law in the context of ethical decision-making. Together with one further source for Chapter 2 (on Princely Government) they demonstrate the strengths and some of the weaknesses of a style of ethics that has shaped papal teaching for centuries.
It will soon emerge that Aquinasās account of natural law faces a number of problems in the modern world in addition to its strengths.
Strengths
Defenders of natural law value it for its emphatic defence of ethical objectivity. According to Aquinas, general or primary principles are unchangeable and normative. Some things, such as theft, adultery and murder, are always wrong. That is, they are objectively wrong. They may clash with other principles at times, but they still remain wrong. Even today most people might agree that, say, genocide, child abuse and slavery are always wrong. That these abuses still happen in the modern world does not make them right. They have sometimes been justified in the past, but that still does not make them right. They are simply wrong.
Another point often made in favour of Aquinas is that he offers a clear path for coping with apparent exceptions. For him exceptions are not really exceptions at all. They are acts that are not what they appear to be. So theft, adultery and murder are always wrong, but if God were to command them in particular instances they would no longer be theft, adultery or murder. Recategorising an act when trying to cope with difficult cases is something that many of us still do. Juries, for example, frequently have to decide whether a particular killing is murder, manslaughter or simply an unfortunate accident.
A third point made about Aquinas is that he allows plenty of room for what today would be termed secular ethics. He emphatically does not claim that only Christians can be ethical. Natural law allows that all people everywhere can be ethical, whether they are Christians or not. Specifically, Christian ethics adds to, but does not subtract from, secular ethics (provided, of course, that secular ethics has been properly stated).
This position could be very attractive for those working in business ethics, bioethics or academic research ethics today. If the ethical principles identified in any of those areas applied only to Christians, non-Christians would simply be off the hook. Non-Christians working in business, medicine or academic research would not need to stick to any ethical requirements.
Yet it is doubtful if many people would be very impressed if their doctor informed them that, as she is not a Christian, there is no need for her to abide by ethical standards in medicine. They might well decide to change their doctor.
Finally, Aquinas offers a clear line of demarcation between philosophy and theology. As a theologian he uses the pre-Christian philosopher Aristotle to provide the philosophical framework for his natural law theory. However, he looks to Christian revelation to establish divine law beyond natural law. For him divine law never contradicts natural law: it adds, not subtracts. Grace crowns nature: grace does not destroy nature.
Weaknesses
Few philosophers today who are not themselves religious make much use of natural law theory. This is despite a renewed interest in ethical objectivity among recent philosophers. Natural law theory seems to have more appeal to Catholic ethicists than to most other ethicists. If someone already believes that God created the world and that Godās good intentions are still evident within this creation, then natural law theory may have considerable appeal (despite the fact that Aristotle himself showed little interest in these beliefs).
A number of problems have been identified in Aquinasās account of natural law. The most obvious problem is getting agreement about the meaning and ethical significance of the word ānaturalā. It will be seen in Chapters 4 and 6 that what he considers to be natural in terms of gender and sexuality is strongly contested today. For instance, he assumes that men by nature are more rational than women, that women are more rational than slaves, and that slaves are more rational than animals. Not exactly 21st century assumptions.
In addition, perhaps there are things today that many of us consider to be natural which will cause equal offence in 900 yearsā time ā for example, our treatment of animals, our laxity about the environment, our resort to wars, or whatever. What is considered to be ānaturalā does seem to have changed over time. Similarly, some medieval āvirtuesā, such as chivalry, no longer seem ānaturalā today.
Another problem is that Aquinas (and Aristotle before him) sees āwell-beingā as the final goal of human beings. Today it is very difficult to get agreement about what constitutes well-being. As already suggested, we might be able to get some narrow agreement about what is objectively wrong, but agreement on what is good for us appears to be much more elusive.
Then there is a problem that troubles both secular philosophers and some Reformed Christian ethicists ā namely whether it really is appropriate to assume that what is ānaturalā is also āgoodā. Philosophers might argue (following Kant) that it is a mistake to derive an āoughtā from an āisā. For them ethical claims cannot safely be derived from scientific descriptions.
To give a blunt example: among lions and some other mammals it is natural for a male to kill the young offspring of an unattached female before forcibly mating with her. When human males today emulate this particular piece of behaviour they are rewarded, if caught and convicted, not with a new pride but with a life sentence for murder and rape.
Some Reformed Christian ethicists also have a problem with assuming that what is ānaturalā is also āgoodā, but for a very different reason. Their objection is theological. In a fallen world, so they argue, we can no longer discern Godās intentions by observing Godās creation. This creation is now too distorted by original and ongoing sin for humans to make any such discernment safely. Instead, people can only know about the good from Godās revelation within the Bible.
This last point suggests a very different approach to ethics than the natural law approach of Aquinas. As already seen, Aquinas does recognise that sin distorts habits and customs and blinds people to what is good. Nevertheless, he still believes that human beings, however sinful, do retain a rational capacity to discern the good. Martin Luther (as will be seen in a moment) was not so convinced.