Kant's Categorical Imperative: The Universal Moral Law

Immanuel Kant’s categorical imperative, developed in his Groundwork of the Metaphysics of Morals (1785) and the Critique of Practical Reason (1788), is one of the foundational concepts of modern moral philosophy. The categorical imperative is the supreme principle of morality, and it provides the foundation for Kant’s deontological ethics. This article examines the central formulations of the categorical imperative, its implications for moral reasoning, and its lasting influence on modern ethics.

The Central Concept

The categorical imperative is the supreme principle of morality, according to Kant. It is “categorical” in that it commands certain actions as necessary in themselves, without reference to any further end. It is “imperative” in that it expresses an obligation that binds the will of the moral agent.

Kant contrasts the categorical imperative with hypothetical imperatives, which command certain actions as means to further ends. The hypothetical imperative says, for example, “If you want to be healthy, you should exercise regularly.” The categorical imperative, by contrast, says, “You should exercise regularly” — without any further justification in terms of the consequences of the action.

The categorical imperative is, for Kant, a principle of reason that is binding on all rational beings. It is not derived from experience, from tradition, or from the will of God; it is derived from the very nature of practical reason itself. The categorical imperative is, in this sense, a priori: it is known independently of experience, and it is binding on all rational beings.

The Formulations

Kant offers several formulations of the categorical imperative, each of which captures a different aspect of the principle.

The Formula of the Universal Law: “Act only according to that maxim by which you can at the same time will that it should become a universal law.”

This formulation captures the idea that moral actions are those that can be universalized. A moral action is one that the agent can rationally will to be a universal law of nature. An immoral action is one that cannot be universalized, because the agent would not be able to will the universal adoption of the maxim.

The test of universalization is rigorous. Lying, for example, cannot be a universal law, because a universal practice of lying would undermine the very institution of trust on which communication depends. Theft, murder, and other violations of the basic principles of morality are ruled out by similar arguments.

The Formula of Humanity: “Act in such a way that you treat humanity, whether in your own person or in the person of any other, always at the same time as an end and never merely as a means.”

This formulation captures the idea that human beings are ends in themselves, and that they should never be treated merely as means to the ends of others. Human beings have a dignity that sets them apart from mere objects, and the proper moral treatment of human beings requires that we respect their dignity.

The Formula of Humanity is an important foundation of the modern doctrine of human rights. The contemporary commitment to the equal moral worth of all human beings, to the protection of human dignity, and to the proper treatment of persons as ends in themselves draw on the central arguments of the Kantian Formula of Humanity.

The Formula of Autonomy: “So act that your will can regard itself at the same time as making universal law through its maxims.”

This formulation captures the idea that the moral agent is autonomous — that the moral law is not imposed on the agent from outside, but is the product of the agent’s own rational will. The moral agent, in Kant’s view, is the author of the moral law, and the proper moral life is one in which the agent governs himself by laws that he has prescribed for himself.

The Formula of Autonomy is an important foundation of the modern concept of moral autonomy. The contemporary commitment to the idea that the moral life requires the development of the agent’s own rational will, and not merely the submission to external authority, is a descendant of the Kantian Formula of Autonomy.

The Formula of the Kingdom of Ends: “Act in accordance with maxims of a universally legislative member of a merely possible kingdom of ends.”

This formulation captures the idea that the moral life is one in which the agent acts as a member of a community of rational beings, all of whom are ends in themselves. The kingdom of ends is a community in which all rational beings are treated as ends, and in which the laws of the community are made by all of the members for all of the members.

The Formula of the Kingdom of Ends is an important foundation of the modern idea of moral community. The contemporary commitment to the idea that moral reasoning requires us to consider the interests of all affected persons is a descendant of the Kantian Formula of the Kingdom of Ends.

The Implications

The categorical imperative has important implications for moral reasoning.

First, it provides a procedure for determining the moral status of particular actions. The agent asks whether the maxim of the action can be universalized, whether the action treats humanity as an end, and whether the action is consistent with the autonomy of the moral agent. If the action passes all of these tests, it is morally permissible; if it fails any of them, it is morally impermissible.

Second, it provides a foundation for the moral law that is independent of experience, tradition, and authority. The categorical imperative is not derived from the consequences of actions, from the will of God, or from the customs of any particular community; it is derived from the very nature of practical reason itself. The moral law, on this view, is binding on all rational beings, regardless of their particular circumstances.

Third, it implies the equal moral worth of all human beings. The Formula of Humanity and the Formula of the Kingdom of Ends both imply that all human beings are ends in themselves, and that they all deserve to be treated with respect. The categorical imperative is, in this sense, a foundation of the modern doctrine of human rights.

The Critiques

The categorical imperative has been criticized from many directions.

The first critique is that the categorical imperative is too abstract. The defenders of this view argue that the formulas of the categorical imperative are too general to provide specific guidance for moral decisions. The test of universalization, in particular, is too formal to determine whether a particular action is morally permissible.

The second critique is that the categorical imperative is too rigid. The defenders of this view argue that the categorical imperative does not allow for the consideration of the consequences of actions, and that this leads to moral judgments that are implausible in particular cases. The Kantian prohibition of lying, for example, is implausible in cases where lying is the only way to prevent serious harm.

The third critique is that the categorical imperative is too demanding. The defenders of this view argue that the categorical imperative sets standards of moral perfection that are impossible for ordinary human beings to meet, and that this leads to moral judgments that are unrealistic and even cruel.

The Legacy

Despite the critiques, the categorical imperative has had a profound influence on the development of modern moral philosophy. The contemporary deontological tradition, represented by writers such as W. D. Ross, Christine Korsgaard, and Onora O’Neill, has developed Kant’s insights in new directions. The contemporary revival of Kantian ethics in the work of John Rawls and the various other political philosophers of the late twentieth century has made Kant a central figure in contemporary moral and political thought.

The Central Concept

The Formulations

The Implications

The Critiques

The Legacy

Further Reading