What does deontology mean?
Deontology is the branch of ethics that locates morality in duty and obligation rather than in outcomes. A deontologist holds that certain actions are right or wrong in themselves — lying, breaking promises, and killing are standard examples — regardless of how much good or harm they produce. The word derives from the Greek deon, meaning 'duty' or 'obligation', combined with logos, 'study', so it literally means 'the study of duty'. Although earlier thinkers such as Samuel Pufendorf wrote on natural-duty ethics, the theory is most closely associated with Immanuel Kant, who grounded morality in the categorical imperative: act only according to principles you could will as universal laws. In modern usage, 'deontology' appears mainly in philosophy seminars, medical ethics committees, and legal debates, usually set in opposition to consequentialism or utilitarianism. The contrast it captures — whether morality is about following rules or achieving good results — remains one of the central questions of practical life.
nounThe branch of ethics concerned with duty and moral obligation, holding that the rightness or wrongness of actions is determined by rules, duties, or principles rather than by their consequences.
- The ethical theory that moral value lies in adherence to duty, obligation, or universal principles rather than in the consequences of actions.
- (More broadly) Any system of ethics centered on rules of obligation — as opposed to consequence- or virtue-based systems.
"As a matter of deontology, she refused to lie even when doing so would have saved lives."
"In a debate dominated by utilitarian reasoning, her argument drew instead on deontology, insisting some acts are simply forbidden."
"Medical ethics often balances deontology against consequentialism: confidentiality is a duty, yet it can be outweighed by serious risk to others."
Rarely pluralized; the plural appears only when comparing distinct duty-based systems or traditions of ethics.
"Comparative ethicists have catalogued several distinct deontologies across religious and philosophical traditions."
Immanuel Kant argued you shouldn't lie even to a murderer at your door asking where his victim is hiding — that's deontology taken to its logical extreme.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of deontology
Deontology comes from the Greek deon (genitive deontos), meaning 'that which is binding, duty or obligation', joined with -logia, 'study or discourse'; it thus means literally 'the study of duty'. The term was coined in English in the early nineteenth century, with Jeremy Bentham using 'Deontology' in the 1830s for the science of morals — an ironic adoption, given Bentham's utilitarianism. Its closest relative is 'ontology', built from the same Greek root on/ontos ('being') with the same suffix, though the two fields are unrelated; the adjective 'deontic', from the same stem, is used in logic to describe modalities of obligation and permission.
Related word forms
How deontology is actually used
A formal, largely academic term used chiefly in philosophy, law, and professional ethics. It rarely appears in casual conversation; speakers more commonly use the adjective form 'deontological'. It is almost always discussed in contrast with consequentialism.
Easily confused with deontology
Deontology judges actions by duties and moral rules regardless of outcome, while consequentialism judges them solely by the results they produce.
Teleology evaluates actions by the ends or purposes they serve, whereas deontology evaluates them by adherence to duty irrespective of ends.