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A maxim is a subjective principle that guides an agent’s action. Kant defines it as “a subjective principle of volition” (or will). By this, he means the idea behind an action, like “stealing is the taking of property that is not mine.” What matters is the maxim and whether you acted out of respect for moral demands in keeping with it.
Kant provides us with the categorical imperative as a means to test if an action is morally correct. As we’ve seen, Kant believes that there is only one categorical imperative, but it can be expressed in multiple ways. We call these ways formulations.
We have already looked at two formulations: the formulation of universal law and the formulation of humanity (also known as the means/ends formulation). The third formulation is the formulation of autonomy. It asks whether the maxim could be endorsed by the agent as a self-legislating rational being. This formulation is the focus of this tutorial.
Kant’s third formulation of the categorical imperative is known as the formulation of autonomy.
"The idea of the will of every rational being as a will that legislates universal law."
It emphasizes the idea that moral agents are authors of the moral law through their rational will.
"Autonomy is thus the ground of the dignity of human nature and of every rational nature."
A few pages later, he provides terminology that helps us see how this idea of the will can be best understood.
Autonomy (autos = self, nomos = law) means self-legislation: acting only on principles one gives to oneself that could rationally be recognized as universally valid. It is not doing “whatever I want”—that would be heteronomy, where one’s choices are determined by inclination, fear, or social pressure. Instead, autonomy is obeying the moral law that reason itself prescribes. Sometimes, people conflate autonomy with freedom, but they are not the same thing for Kant. While freedom refers to the capacity to choose, autonomy in Kant’s sense is the rational self-governance that gives moral law to that freedom.
British philosopher Onora O’Neill stresses that Kant’s autonomy is not about “self-expression” or “choosing for oneself” in any arbitrary sense; instead, it is about acting on principles that have a universalizable form ("Autonomy and the Emperor’s New Clothes", 2003). Autonomy is formal: The key question is whether the principle of one’s action can be considered to be the law for everyone.
This formulation shifts the focus from external universalization (Formulation 1) and interpersonal respect (Formulation 2) to the internal authority of the moral agent. The moral law is not imposed from the outside; it arises from the rational nature of the agent themselves.
The formulation of autonomy is crucial because of the following reasons:
"The autonomy of the will is the sole principle of all moral laws and of the duties conforming to them."
For Kant, genuine autonomy requires that, at the point of action, one could genuinely do something else, making freedom essential for moral responsibility. This formulation of autonomy also lays the foundation for Kant’s later political and legal philosophy, where autonomy becomes the basis for rights and duties in a moral community.
Kant insists these are equivalent in meaning, though they emphasize different aspects of moral reasoning. Review this table to see how they compare.
| Formulation | Application |
|---|---|
| Universal Law | Focuses on whether a maxim can be willed as a universal law (that is, whether it can be consistently adopted by all rational agents) |
| Humanity | Focuses on whether a maxim respects the humanity in others (that is, whether it treats others as ends in themselves, and not merely as means) |
| Autonomy | Focuses on whether a maxim can be endorsed by the agent as a law they make for themselves |
"The ground of all practical lawgiving lies (in accordance with the first principle) objectively in the rule and the form of universality . . . subjectively, however, it lies in the end; but the subject of all ends is every rational being as an end in itself."
In this quote, Kant explains how these versions all coexist.
It can be useful to see how the same maxim fails when tested by each of the three formulations we have considered. Throughout Groundwork, Kant famously uses the example of someone considering making a false promise with no intention of keeping the promise. This is often understood to be falsely promising to repay a loan in order to secure money. We can use the idea of a false promise to see in which ways the maxim fails.
IN CONTEXT
Maxim: Falsely promising to repay a loan in order to secure money.
Formulation Application Universal Law A maxim of making a false promise cannot be universalized because the institution of promising would collapse. Humanity It treats the other person merely as a means to securing a loan, not as an end in themselves. Autonomy It cannot be willed as a self-given law, because doing so undermines the trust and mutual recognition necessary for rational lawgiving.
Thus, we can see that these three formulations are really all different understandings of the same test, which is to say they are different aspects of the categorical imperative.
Now, let’s try to apply this formulation. First, identify a maxim. Then ask, “Can I will this maxim as a law I give myself, consistent with my status as a rational legislator?” Let’s see how this works together.
To begin, let’s look at an example about money.
IN CONTEXT
Maxim: Refusing to help others (“I will live only for myself and never aid others,” from Groundwork, 4:423)
Application: This maxim fails since it denies mutual dependence and respect among legislators.
Maxim: Neglecting your own talents (“I will let my talents rust rather than develop them,” from Groundwork, 4:423)
Application: This maxim fails since rational self-legislators must cultivate the capacities that make legislation possible.
Next, let’s look at an example about a contemporary issue.
IN CONTEXT
Maxim: “When convenient, I will ignore environmental responsibility.”
Application: This maxim fails not only because it cannot be universalized (indeed, its framing shows that it is hypothetical), but also because it undermines the very idea of oneself as a rational self-legislator. To act autonomously, one must see oneself as giving law to one’s will that could be endorsed from the standpoint of reason. A law that privileges momentary convenience over the conditions necessary for the continued exercise of rational agency (such as a stable climate and habitable environment) contradicts the agent’s own status as autonomous.
By choosing convenience over environmental responsibility, the agent is effectively saying, “My short-term comfort matters more than the long-term well-being of others and even myself as a future rational agent.” This violates the idea of autonomy because it refuses to legislate from the standpoint of a universal community of ends. It undermines the shared conditions, like a livable planet, that make moral agency possible for everyone.
Finally, let’s look at how Kant develops the idea of autonomy further in his later works.
"The moral law is the law of autonomy of the will."
Here, Kant explicitly identifies moral law with autonomy. He says that moral law is not imposed from the outside, but arises from the rational will itself. In this later work (written 3 years after Groundwork), Kant reinforces that morality is grounded in the self-governance of rational agents. Morality is something that we give to ourselves through reason.
"Freedom (independence from being determined by alien causes) is the property of the will that makes it a law to itself."
Twelve years after Groundwork, Kant published his work Metaphysics of Morals. Groundwork was not an introduction to this later book, but a necessary step in explaining morality. In this quotation from the later book, Kant is connecting the idea of freedom itself to autonomy. Freedom and morality are inseparable. To be free is to be autonomous and to be autonomous is to be a moral agent, because the will freely gives itself moral law.
Autonomy becomes the cornerstone of Kant’s moral philosophy, linking ethics, freedom, and dignity. The third formulation of the categorical imperative is foundational for his eventual expansion of the importance of not just obeying moral laws but being the source of those laws themselves. His understanding of autonomy in Groundwork also anticipates his political theory, where autonomous individuals form a kingdom of ends, or a moral community governed by laws they give themselves.
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REFERENCES
O’Neill, O. (2003). Autonomy: The emperor’s new clothes. Proceedings of the Aristotelian Society, Supplementary Volumes, 77(1), 1–21. https://doi.org/10.1111/j.0066-7373.2003.00054.x
