A family of normative moral theories that determine the moral status of actions primarily by their conformity to duties, rules, or rights—grounded in principles intrinsic to the action or agent’s role—rather than by the consequences those actions produce.

Principle

An action’s moral rightness is given by its accordance with justified duties or rules; consequences do not by themselves establish moral status.

Demonstration

Illustrative scenario → A clinician believes they have a professional duty of honesty. A patient asks directly whether a terminal prognosis is accurate. The clinician, following duty-based reasons, discloses the prognosis truthfully even if a lie might temporarily improve the patient’s mood. The clinician’s action is judged by conformity to the duty to be truthful, not by the ensuing emotional outcome.

Misapplication

Mistakenly treating any rule-following as deontological: one may assume that mere obedience to arbitrary or unjustified rules counts as deontology. The semantic error is failing to distinguish between justified moral duties (theory‑dependent) and any rule issuance; deontology requires norms grounded in moral reasons, not formal compliance alone.

Consequence

Correct application centers moral deliberation on justifying duties, producing action-guidance that can mandate duties even when outcomes seem suboptimal; practically, this yields stable constraints on action but may generate conflicts between duties or outcomes.

Reversal

When duties conflict or when the specification of duties depends on wider empirical or institutional facts, the simple rule‑conformity principle requires qualification (e.g., priority rules, prima facie duties, or domain-specific role obligations); in such cases moral assessment invokes higher-order principles about how to resolve duty conflicts.

Boundary

Clearly within: moral judgments grounded explicitly in duties or rights (e.g., a prohibition against lying justified as a duty). Boundary case: rule‑consequentialism—uses rules because of their long-term consequences but frames justification in terms of outcomes, so it resembles deontology superficially. Clearly outside: theories that evaluate acts solely by aggregate outcomes (consequentialism).

Semantic Tension

Tension with Consequentialism over whether outcomes or duties determine right action; tension with Virtue Ethics over whether rules or character play the primary justificatory role.

Synthesis

Deontological ethics shifts moral authority from outcome-calculation to normative claims about what one ought to do, producing clear constraints and duties but requiring secondary mechanisms to handle duty conflicts and specification.