I. Definition

Deontology is a school of moral philosophy in which ethical behavior equals following rules. Deontologists believe that the goal of moral philosophy should be to figure out the “rules” for living a moral life and that once people know those rules they should follow them. “The Golden Rule” (do unto others as you would have them do unto you) is an example of deontology; it’s a moral rule meant to be followed in all situations, for everyone to live moral lives.

In general, the goal of deontology is to create a rational set of rules, but this isn’t always the case. Some people base their deontology on faith rather than rationality.


II. Types of Deontology

People often think of deontology as a rigid or absolutist school of thought, but in fact this isn’t necessarily true either. In fact, deontology can be either universal or relative:

a. Deontological Universalism

The rules apply to everyone, under all circumstances.


If you’re a Hindu you might believe that it’s wrong to eat beef; this rule would be part of your deontology. If you thought it was wrong for anyone to eat beef, you’d be a deontological universalist.

b. Deontological Relativism

The rules apply to people under certain circumstances, or within certain traditions.


You might feel that it was wrong for you, as a Hindu, to eat beef, but OK for non-Hindus to eat beef; then you’d be a deontological relativist.

The advantage of relativism is its flexibility; it makes it easier to live in a diverse world where other people have beliefs and practices different from your own. On the other hand, some people feel that it’s too flexible. They want a more solid moral philosophy, one that judges right from wrong for everyone.

Deontology can also be either religious or secular:

Religious Secular
Universalist God(s) has/have determined a set of rules for humanity. These rules apply to everyone, at all times. Morality is based on a set of rules, but these rules do not come from any God. Instead, they come from reason, compassion, or nature.
Relativist God(s) has/have determined a set of rules for believers to follow, but the same rules don’t necessarily apply to everyone in all situations. There are rules for behavior, but they depend on our circumstances and culture. These rules come from society, not from God, but they are still important moral rules nonetheless.


III. Deontology vs. Consequentialism vs. Virtue Ethics

Deontology is usually contrasted with consequentialism and virtue ethics, the other two main branches of Western moral philosophy. These branches do not exactly compete; think of them more as different lenses focusing on different aspects of morality. Some people emphasize one or another, but that doesn’t mean they deny the importance of the others.

Deontology Consequentialism Virtue Ethics

Morality is about finding good rules.


We should come up with a system of rules to guide our behavior and stick by it.

Morality is about outcomes.


We should assess the most likely results of our actions and choose the actions with the best results.

Morality is about good people.


We should work on becoming more honest, compassionate, kind, courageous, etc. As we  become more virtuous, we’ll make more ethical choices and won’t need rules.


IV. Famous Quotes About Deontology

Quote 1

“Do what is right, though the world may perish.” (Latin Proverb)

This proverb is a favorite of deontologists. It’s a strong bone of disagreement with consequentialists, who would say that letting the world perish is the opposite of doing what’s right! But for deontologists, morality is not defined by consequences, so a good action may have disastrous results; but that doesn’t change the fact that it was the right thing to do. Consequentialists say that this is a dangerous philosophy because it allows people to justify horrible things, but deontologists reply that this is unlikely so long as the rules are true and just.

Quote 2

“Non-violence leads to the highest ethics, which is the goal of all evolution. Until we stop harming all other living beings, we are still savages.” (Thomas A. Edison)

Thomas Edison was the inventor of the lightbulb and numerous other devices (several of which may have been stolen from less famous inventors!) He lived in America at a time when there was intense interest in Eastern religions such as Hinduism and Buddhism. Edison’s own ethical beliefs were heavily influenced by the Hindu / Buddhist concept of ahimsa, or non-violence; he believed that a commitment to do no harm to other living things could lead to a completely ethical code of behavior.


V. The History and Importance of Deontology

Deontology has rarely been separated from virtue ethics. Most moral and religious traditions combine these two approaches.


Judaism, Christianity, and Islam all believe in their own versions of the Ten Commandments, given to Moses by God in the Old Testament; this is obviously a deontological system—a set of rules. However, all these religions also emphasize the importance of virtue, urging believers to develop their honesty, generosity, and compassion.

Deontology became prominent during the Enlightenment, when thinkers such as Immanuel Kant tried to develop moral systems independent of religion. These thinkers had witnessed centuries of religious violence and intolerance in Europe, and many believed that it was time to develop a new approach to morality. They were not necessarily anti-Christian (though some were), but they all agreed that Christianity needed to be supplemented with ethical rules based on reason rather than faith and tradition.

This side of the Enlightenment was popular in France and Germany, but less so in Britain and America. In Britain and America, consequentialism dominated — specifically, a branch of consequentialism called utilitarianism, which focuses on promoting maximum happiness for all. But that changed when John Rawls made a famous argument in A Theory of Justice that convinced many people to abandon utilitarianism. Rawls was a Kantian who argued for an Americanized version of German deontology. As a result of Rawls’s work, secular deontology has become highly influential in American philosophy departments, although utilitarianism still has a lot of followers.


VI. Deontology in Popular Culture

Example 1

In Mass Effect, Legion is the name given to a walking hive-mind made out of over a thousand “geth” computer programs. Although the geth are usually evil, this particular hive-mind has a moral compass based on a system of rules. All of the different programs have agreed on a “code of laws” for their behavior, and Legion refers back to this code when making moral decisions.

Example 2

The Jedi Code is a set of rules guiding all Jedi in the Star Wars universe. When they stray from this Code, the Jedi can be seduced by the dark side of the Force. It includes rules like controlling one’s emotions and avoiding harm to other living beings. The Jedi seem to guide their behavior as much as possible according to these rules, making them deontologists.


VII. Controversies

The Categorical Imperative

In the field of deontology, the most famous theory is Immanuel Kant’s Categorical Imperative. This is a complex and controversial idea; it claims that we should always act according to the same rules that we rationally want everyone else to follow.


We shouldn’t break promises because we can’t rationally want everyone to do so; if everyone broke their promises all the time, then the whole idea of a promise would no longer make any sense; therefore a world of broken promises is not only undesirable but also irrational.

The Categorical Imperative has attracted both followers and critics over the centuries. The main criticism is that it doesn’t give real answers to many ethical questions. For example, what if somebody says they want to live in a world of brutal, violent competition in which the strongest emerge on top and the weak are destroyed? This is the world that the Nazis sought to create. Most people say that such a world is undesirable, but it’s not easy to prove that it’s irrational. What would you say to somebody who tells you that this is, in fact, the world that they want? How would we argue against a Nazi using the Categorical Imperative? Critics say that if a moral idea does not show how Nazism is wrong, then there is something wrong with the idea.


Which of the following is NOT one of the major strands in Western moral philosophy?





Which of the following best describes deontology





Deontology can be subdivided in many ways. One way is ___ vs. ___.





For most of its history, deontology was more popular in ____ and less popular in America and Britain.






  1. Reply

    Excellent material.

  2. Reply

    Clear and understandable explanations. Thank you!

  3. Reply

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