A deontic principle originating in Kantian ethics that requires agents to act only according to maxims they can will to become universal law; it identifies moral duty as grounded in reason and independent of contingent desires or outcomes.

Principle

An action is morally required if and only if the agent can consistently will the maxim guiding the action to be a universal law for all agents in comparable circumstances; moral demands are therefore unconditional (categorical) rather than hypothetical.

Demonstration

Illustrative Scenario → Recognition → Action → Consequence: An agent considers making a false promise to secure a loan. Formulating the maxim ('I will make false promises to obtain money when convenient') and asking whether one could will it as a universal law reveals that universal adoption would frustrate the institution of promising; the test indicates the maxim fails, so the action is impermissible under the principle.

Misapplication

Treating the categorical imperative as a generic injunction to ‘act universally’ without specifying the maxim’s formulation or conflating categorical imperatives with hypothetical (means‑end) imperatives; such misuse obscures whether the willability test has been applied to the relevant principle.

Consequence

Provides a procedure for evaluating duties that centers on rational consistency and the form of maxims rather than on consequences; it grounds obligations that claim independence from agents’ contingent aims.

Reversal

The simple formulation does not by itself resolve conflicts between competing categorical demands or specify how to formulate sufficiently precise maxims; in contexts where maxims are underdetermined or duties clash, further interpretive resources or principles are required to settle obligations.

Boundary

Clearly within: deontic duties purportedly independent of contingent desires and assessed by the willability of maxims. Boundary case: rules that mix means with ends (practical rules) where the categorical test is ambiguous. Clearly outside: hypothetical imperatives that prescribe actions as means to particular ends.

Semantic Tension

Universality (formalist duty) ↔ Consequentialism (outcome‑based justification): the categorical imperative emphasizes form and rational willability while consequentialist accounts evaluate actions by aggregated outcomes.

Synthesis

The categorical imperative reframes moral evaluation as a test of whether the principle motivating an action could coherently be endorsed as a law for all agents; its application requires careful formulation of maxims and attention to possible conflicts among duties.