Kantian ethics: duty and persons as ends
- Theory
For Kant, an act has moral worth if done from duty, and every person is always treated as an end and never merely as a means.
What it is
Immanuel Kant (Groundwork of the Metaphysics of Morals, 1785) held that the only thing good without qualification is a good will: willing to act out of respect for the moral law. An act has moral worth when it is done from duty, not merely in accordance with duty out of interest or inclination. The moral law is expressed in the categorical imperative, which binds every rational being regardless of their desires, unlike hypothetical imperatives («if you want X, do Y»). Its main formulas are: act only on maxims you could will as universal law; treat humanity, in yourself and in others, always as an end and never merely as a means; and act as a legislating member of a kingdom of ends. The dignity of the person comes from their rational autonomy. This page goes deeper than the summary in «Ethical theories in brief».
Core ideas
- From duty versus in accordance with duty: a doctor who is honest only for fear of a lawsuit acts in accordance with duty, but without full moral worth.
- Universalisation test: a maxim that cannot be conceived as universal law without contradiction gives rise to a perfect duty.
- Humanity as an end: using others as a means is acceptable only if they could consent to it.
- Autonomy: the moral law binds because each rational being gives it to themself; hence dignity.
- Kingdom of ends: acting as a member of a community of persons who legislate for one another.
The formulas of the categorical imperative
| Formula | What it asks | Clinical example |
|---|---|---|
| Universal law | Act only on maxims that can be universalised | Do not lie on a certificate: if everyone did, certificates would be worthless |
| Humanity | Treat the person always as an end, never merely as a means | Ask for consent before enrolling someone in a study |
| Autonomy | See one's own will as a universal lawgiver | Respect the reasoned decision of a patient with capacity |
| Kingdom of ends | Act as a member of a community of equal persons | Institutional rules that everyone affected could accept |
In clinical practice
- Informed consent expresses the formula of humanity: without it, the patient is used merely as a means to someone else's end.
- In research, enrolling a person without consent to benefit others violates their dignity even if the result is useful.
- Deceiving a patient «for their own good» treats their reason as an obstacle: Kantian ethics demands truthfulness.
- Promising and not delivering (for example, a follow-up visit) cannot be universalised: it would destroy trust in promises.
Criticisms and limits
- Rigidity with conflicting duties: if two perfect duties clash, the theory gives little guidance.
- Kant held that one must not lie even to a murderer asking where the victim is, a conclusion many reject.
- Grounding dignity in reason raises doubts about beings without rational autonomy (infants, people with advanced dementia, animals).
- It pays little attention to consequences, which matter a great deal in medicine and public health.
- In Colombia, the Constitution founds the State on respect for human dignity (art. 1), an idea close to the formula of humanity.
Test yourself
Think of the answer, then tap the question to see it.
What is the only thing good without qualification according to Kant?
A good will, that is, willing to act out of respect for the moral law.
What is the difference between a categorical and a hypothetical imperative?
The categorical one binds every rational being unconditionally; the hypothetical one binds only if a given end is wanted («if you want X, do Y»).
What does the formula of humanity ask?
To treat humanity, in yourself and in others, always as an end and never merely as a means.
Why is informed consent an example of Kantian ethics?
Because without consent the patient is used merely as a means to someone else's end; asking for it respects their rational autonomy and dignity.
What is a classic criticism of Kantian ethics?
Its rigidity when duties clash, as in Kant's refusal to lie even to a murderer asking where the victim is.
Connections
Educational content on ethics and health law; not legal advice. Laws and case law change: each page links the official text and says when it was last checked. For a real case, read the text in force and ask a lawyer or the medical ethics tribunal.
Sources: Kant's Moral Philosophy (Stanford Encyclopedia of Philosophy, 2025); Constitución Política de Colombia 1991 (Función Pública, Gestor Normativo, 1991).
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Representative model, for educational purposes only.