Categorical Imperative
Kant's supreme principle of morality: act only on a maxim you can will as a universal law for all rational agents.
The categorical imperative is the central principle of Immanuel Kant's moral philosophy, articulated in the Groundwork of the Metaphysics of Morals (1785). Kant distinguishes hypothetical imperatives, which prescribe means to ends one happens to want, from the categorical imperative, which prescribes what reason itself requires of any rational will.
Kant offers several formulations: the universal law formulation (act only on that maxim through which you can at the same time will that it become a universal law); the formula of humanity (treat humanity, whether in your own person or in that of another, always as an end and never merely as a means); and the formula of autonomy (act as if you were a legislating member of a kingdom of ends). The three formulations are meant to express the same principle from different angles. The categorical imperative remains the canonical alternative to utilitarian and virtue-ethical accounts of moral action.
Kant's three formulations are not three separate principles but three angles on the same demand of practical reason. The universal-law formulation tests whether a maxim could function as a law for all rational agents. The humanity formulation requires that no person be reduced to an instrument of another's will. The autonomy formulation completes the picture by making each rational will the legislator of the moral order it inhabits.
The categorical imperative has been the principal modern target of consequentialist criticism. Mill argued that the universal-law test secretly relies on consequence-based reasoning to discriminate acceptable from unacceptable maxims. Hegel charged that the test is empty — that any maxim, suitably reformulated, could pass it. Twentieth-century neo-Kantians from Christine Korsgaard to Onora O'Neill have defended Kant against both objections by reading the imperative as a constitutive principle of rational agency rather than a decision procedure.
How philosophers have framed categorical imperative
| Philosopher | Position |
|---|---|
| Immanuel Kant | The supreme principle of morality binding any rational will. |
| Georg Wilhelm Friedrich Hegel | Empty formalism; the test cannot discriminate among substantive maxims. |
| John Stuart Mill | Covertly relies on consequence-based reasoning; utility is the real criterion. |
| John Rawls | Reframed as a procedural test in the original position behind the veil of ignorance. |
| Friedrich Nietzsche | Refined slave morality; universalization disguises resentment as reason. |
Representative quotes
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Immanuel Kant
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“Two things fill the mind with ever new and increasing admiration and awe, the more often and steadily we reflect upon them: the starry heavens above me and the moral law within me.”
Two things fill the mind with ever-increasing wonder and awe, the more often and the more intensely the mind of thought is drawn to them: the starry heavens above me and the moral law within me.
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Georg Wilhelm Friedrich Hegel
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“Nothing great in the world has been accomplished without passion.”
Often abbreviated to: Nothing great in the World has been accomplished without passion. | Variant translation: We may affirm absolutely that nothing great in the world has ever been accomplished without enthusiasm.
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John Stuart Mill
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“It is better to be a human being dissatisfied than a pig satisfied; better to be Socrates dissatisfied than a fool satisfied.”
Ch. 2
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John Rawls
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“Each person is to have an equal right to the most extensive basic liberty compatible with a similar liberty for others.”
Chapter II, Section 11, pg. 60
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Christine Korsgaard
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Attributed to Christine Korsgaard:
“The reflective structure of human agency is the source of normativity.”
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