Persons and Things
Kant draws a fundamental divide between things and persons. Things have conditional worth — they are valuable insofar as they serve some purpose, and can always in principle be replaced by something of equivalent utility. Persons are different. Their existence is not conditional on their usefulness. They are rational beings, and rational beings are ends in themselves — they carry their worth within them.
rational beings, on the contrary, are called persons, because their very nature points them out as ends in themselves, that is as something which must not be used merely as means, and so far therefore restricts freedom of action (and is an object of respect).
Never Merely as a Means
The formula does not forbid using others in the ordinary sense — we use the baker to get bread, the doctor to get treatment. What is forbidden is treating someone merely as a means: using them in a way that bypasses or overrides their rational agency, as when we deceive them or coerce them. The key word is "merely." We may use people while also respecting them as rational agents with their own purposes.
So act as to treat humanity, whether in thine own person or in that of any other, in every case as an end withal, never as means only.
The Ground of Human Dignity
This formulation grounds Kant's account of human dignity. Because rational nature is an end in itself, it cannot be assigned a price — it is beyond all valuation. This is why no calculation of consequences, however favourable, can justify treating a person merely as an instrument. The formula of humanity gives moral force to the intuition that some things simply cannot be done to people, whatever the outcome.
The formula of humanity appears in the Second Section of the Groundwork, where Kant tests it against the same four examples he uses for the formula of universal law.
Related Concepts
