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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 if 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 three formulations: the formulation of universal law, the formulation of humanity (also known as the means/ends formulation), and the formulation of autonomy. The fourth formulation is the formulation of the kingdom of ends. It asks whether the maxim could be adopted as moral law in a community where all act in accordance with the categorical imperative. This formulation is the focus of this tutorial.
Kant’s fourth formulation of the categorical imperative is known as the formula of the kingdom of ends. It envisions a moral community—a kingdom—where all rational beings both create and obey universal moral laws. He defines it as follows: “Act according to maxims of a universally legislating member of a merely possible kingdom of ends” (Groundwork, 4:439).
This formulation integrates the ideas of universality, respect for people, and autonomy into a single vision of moral life. In the kingdom of ends, each person treats others not merely as means, but as fellow legislators of moral law. This “merely possible” kingdom refers to an idealized moral community—not necessarily one that exists, but one that we can strive toward.
The kingdom of ends is thus where morality becomes collective: It asks not only whether a maxim is rational for oneself, but also whether it can belong to a system of laws shared by all rational beings.
The kingdom of ends formulation is important because of the following reasons:
"In the kingdom of ends everything has either a price or a dignity. What has a price can be replaced by something else as its equivalent; what on the other hand is above all price, and therefore admits of no equivalent, has a dignity."
People have dignity because they are capable of moral legislation. This formulation shows that morality is not just about individual actions, but about building a world where all rational beings are respected as ends in themselves. Thus, morality is not only about individual duty or personal dignity; it is about constructing a world where the dignity of all is realized.
Kant presents four formulations of the categorical imperative, each highlighting a different aspect of moral reasoning. Though distinct in emphasis, they are equivalent in meaning.
| Formulation | Application |
|---|---|
| Universal Law | Can your maxim be universalized without contradiction? |
| Humanity | Does your maxim treat others as ends, not merely as means? |
| Autonomy | Can you will your maxim as a law you give yourself? |
| The Kingdom of Ends | Can your maxim be endorsed in a community of rational moral legislators? |
"The ground of all practical lawgiving lies 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."
Together, these formulations express the same moral principle: Rational beings must act only on maxims that could be shared and endorsed by all as members of a moral community. It is useful to see how the same maxim is considered through the lens of each formulation so we can appreciate how each version emphasizes different aspects.
If we look back at Kant’s running example of someone making a false promise, we can see how each formulation would evaluate the maxim.
IN CONTEXT
Maxim: Someone considering making a false promise with no intention of keeping the promise
Formulation Application Universal Law Universalized, promises would collapse; self-defeating Humanity Uses others merely as tools Autonomy Undermines one’s role as a self-legislator The Kingdom of Ends Cannot belong to a community where trust is necessary for lawgiving
If we want to think about a more contemporary example, we can think about evaluating the actions of someone who is considering using personal data received by hacking into systems.
IN CONTEXT
Maxim: I will use personal data without consent for my convenience.
Formulation Application Universal Law Universalized, trust in systems collapses Humanity Denies others’ status as ends with control over their information Autonomy Contradicts lawgiving by undermining the conditions for rational agency The Kingdom of Ends Cannot be part of a shared moral community where agents participate equally in decisions affecting their lives
Thus, we can see that these four formulations are really all different understandings of the same test, which is to say different aspects of the categorical imperative. Though each formulation emphasizes a different perspective (logical consistency, interpersonal respect, self-governance, and communal endorsement), they all reflect the same underlying moral principle.
Now, let’s try to apply this formulation. First, identify a maxim. Then ask, “Could this maxim be endorsed by all rational beings as fellow legislators?” Finally, check, “Does this maxim respect the dignity and autonomy of others?” It may be useful to look at two other examples from Kant.
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 treats others as tools, not as fellow legislators.
Maxim: Neglecting your own talents (“I will let my abilities lie dormant rather than develop them,” from Groundwork, 4:423)
Application: This maxim fails because it harms the collective good, treats one’s own rational nature as a means, undermines autonomy, and weakens the moral community.
Next, let’s look at an example about a contemporary issue.
IN CONTEXT
Maxim: “I will not contribute time or effort to community programs, even when I can, because it is inconvenient.”
Application: This maxim fails against the fourth formulation because it undermines a shared moral community. Understanding how this undermines requires thinking about this, in part, from the lens of the first formulation. If the maxim were universalized (and thereby became moral law in the kingdom of ends), no one would contribute to community programs. This would effectively end what it means to be a community, and we would not have a kingdom of ends.
Alternatively, we could consider the following maxim: “I will contribute to community programs when I am able.” (There is some question about whether “when I am able” would move this into a hypothetical imperative. If this worries you, one could stick with “I will contribute to community programs.”) If we were in the kingdom of ends, everyone would be able to take this action, and the shared effort would strengthen the moral fabric of society.
Finally, let’s look at how Kant’s idea of the kingdom of ends is also reinforced in his later writings.
"Freedom (independence from being determined by alien causes) is the property of the will that makes it a law to itself."
The kingdom of ends is the culmination of Kant’s moral philosophy, where freedom, dignity, and law converge in a shared moral world.
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