Deontology and Ethics

Ethics as Obedience to Duty and God

Moral compass
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Deontology (or Deontological Ethics) is the branch of ethics in which people define what is morally right or wrong by the actions themselves, rather than referring to the consequences of those actions, or the character of the person who performs them. The word deontology comes from the Greek roots deon, which means duty, and logos, which means science. Thus, deontology is the "science of duty."

Deontological moral systems are characterized by a focus upon and strict adherence to independent moral rules or duties. To make the correct moral choices, one must understand what those moral duties are and what correct rules exist to regulate those duties. When the deontologist follows his or her duty, he or she is by definition behaving morally. Failure to follow one's duty makes one immoral.

In a deontological system, duties, rules, and obligations are determined by an agreed-upon code of ethics, typically those defined within a formal religion. Being moral is thus a matter of obeying the rules laid out by that religion.

The Motivation of Moral Duty

Deontological moral systems typically stress the reasons why certain actions are performed. Simply following the correct moral rules is often not sufficient; instead, one must have the correct motivations as well. A deontologist is not considered immoral even though they have broken a moral rule, as long as they were motivated to adhere to some correct moral duty (and presumably made an honest mistake).

Nevertheless, a correct motivation alone is never a justification for an action in a deontological moral system. It cannot be used as a basis for describing an action as morally correct. It is also not enough to simply believe that something is the correct duty to follow.

Duties and obligations must be determined objectively and absolutely, not subjectively. There is no room in deontological systems of subjective feelings. On the contrary, most adherents condemn subjectivism and relativism in all their forms.

The Science of Duty

In most deontological systems, moral principles are absolute. In particular, that means that moral principles are completely separate from any consequences which following those principles might have. Thus, if the set of values includes the proviso that it is a sin to lie, then lying is always wrong—even if that results in harm to others. A deontologist following such strict religious principles would be acting immorally if she or he lied to Nazis about where Jews were hiding.

Key questions which deontological ethical systems ask include:

  • What is the moral duty?
  • What are my moral obligations?
  • How do I weigh one moral duty against another?

Examples of Deontology

Deontology is thus a theory of moral obligation, and it encompasses moral theories that emphasize a person's rights and duties. The term was coined by Jeremy Bentham in 1814, and he believed that deontology was a way to marshall self-interested reasons for agents to act for the general good, but Bentham believed that following a strict moral code of behavior was in fact for the general good of humankind. Modern deontologists focus more attention on individual rights and duties. In these fairly simple-minded examples, decisions that might be made by a hypothetical Deontologist are compared to those of a hypothetical Consequentialist.

  • A group of terrorists is holding two hostages and threatening to kill them both unless you kill a third person.

The Consequentialist would kill the third person because by doing so you minimize the outcome (fewer dead people). The Deontologist would not kill the third person because it is never right that you should kill anyone, regardless of the outcome.

  • You are walking in the woods and you have snake venom antidote in your backpack. You come across a person who has been bitten by a snake and you recognize the person as one proven to be responsible for a series of rapes and killings.

The Deontologist gives the antidote to the person because it saves a life; the Consequentialist withholds the medication because to do so potentially saves many others.

  • Your mother has Alzheimer's disease and every day she asks you if she has Alzheimer's disease. Telling her "yes" makes her miserable for that day, then she forgets what you told her and asks you again the next day.

The Deontologist tells her the truth because lying is always wrong; the Consequentialist lies to her because they will both enjoy that day.

  • You love to sing show tunes at the top of your voice, but your neighbors complain about it.

The Deontologist stops singing because it is wrong to impinge on other people's right to not hear you; the Consequentialist stops singing to avoid retaliation.

These arguments are what ethics professor Tom Doughtery calls "agent-based" arguments by the Deontologist and Consequentialist because they are set up for one person's actions: moral ethics for the deontologist may instead make one prevent anyone else from killing the third stranger, withholding snake venom, lying to your mother, or singing show tunes at the tops of their voices. 

In addition, notice that the consequentialist has more options: because they weigh what is the cost of a particular choice.

Types of Deontological Ethics

Some examples of deontological ethical theories are:

  • Divine Command—The most common forms of deontological moral theories are those which derive their set of moral obligations from a god. According to many Christians, for example, an action is morally correct whenever it is in agreement with the rules and duties established by the Christian God.
  • Duty Theories—An action is morally right if it is in accord with a given list of duties and obligations.
  • Rights Theories—An action is morally right if it adequately respects the rights of all humans (or at least all members of a given society). This is also sometimes referred to as Libertarianism, in that people should be legally free to do whatever they wish so long as their actions do not encroach upon the rights of others.
  • Contractarianism—An action is morally right if it is in accordance with the rules that rational moral agents would agree to observe upon entering into a social relationship (contract) for mutual benefit. This is also sometimes referred to as Contractualism.
  • Monistic Deontology—An action is morally right if it agrees with a single deontological principle which guides all other subsidiary principles.

Conflicting Moral Duties

A common criticism of deontological moral systems is that they provide no clear way to resolve conflicts between moral duties. A purely deontological moral system cannot include both a moral duty not to lie and one to keep others from harm.

In the situation involving Nazis and Jews, how is a person to choose between those two moral duties? One response to that might be to simply choose the "lesser of two evils." However, that means relying on knowing which of the two has the least evil consequences. Therefore, the moral choice is being made on a consequentialist rather than a deontological basis.

According to this argument, duties, and obligations set forth in deontological systems are actually those actions which have been demonstrated over long periods of time to have the best consequences. Eventually, they become enshrined in custom and law. People stop giving them or their consequences much thought—they are simply assumed to be correct. Deontological ethics are thus ethics where the reasons for particular duties have been forgotten, even if things have completely changed.

Questioning Moral Duties

A second criticism is that deontological moral systems do not readily allow for gray areas where the morality of an action is questionable. They are, rather, systems which are based upon absolutes—absolute principles and absolute conclusions.

In real life, however, moral questions often involve gray areas rather than absolute black and white choices. We typically have conflicting duties, interests, and issues that make things difficult.

Which Morals to Follow?

A third common criticism is the question of just which duties qualify as those which we should follow, regardless of the consequences.

Duties which might have been valid in the 18th century are not necessarily valid now. Yet, who is to say which ones should be abandoned and which are still valid? And if any are to be abandoned, how can we say that they really were moral duties back in the 18th century?


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Cline, Austin. "Deontology and Ethics." Learn Religions, Sep. 10, 2021, Cline, Austin. (2021, September 10). Deontology and Ethics. Retrieved from Cline, Austin. "Deontology and Ethics." Learn Religions. (accessed March 28, 2023).