Towards the end of his most influential work, Critique of Pure Reason(1781/1787), Kant argues that all philosophy ultimately aims at answering these three questions: “What can I know? What should I do? What may I hope?” The book appeared at the beginning of the most productive period of his career, and by the end of his life Kant had worked out systematic, revolutionary, and often profound answers to these questions.
At the foundation of Kant’s system is the doctrine of “transcendental idealism,” which emphasizes a distinction between what we can experience (the natural, observable world) and what we cannot (“supersensible” objects such as God and the soul). Kant argued that we can only have knowledge of things we can experience. Accordingly, in answer to the question, “What can I know?” Kant replies that we can know the natural, observable world, but we cannot, however, have answers to many of the deepest questions of metaphysics.
Kant’s ethics are organized around the notion of a “categorical imperative,” which is a universal ethical principle stating that one should always respect the humanity in others, and that one should only act in accordance with rules that could hold for everyone. Kant argued that the moral law is a truth of reason, and hence that all rational creatures are bound by the same moral law. Thus in answer to the question, “What should I do?” Kant replies that we should act rationally, in accordance with a universal moral law.
Kant also argued that his ethical theory requires belief in free will, God, and the immortality of the soul. Although we cannot have knowledge of these things, reflection on the moral law leads to a justified belief in them, which amounts to a kind rational faith. Thus in answer to the question, “What may I hope?” Kant replies that we may hope that our souls are immortal and that there really is a God who designed the world in accordance with principles of justice. In addition to these three focal points, Kant also made lasting contributions to nearly all areas of philosophy. His aesthetic theory remains influential among art critics. His theory of knowledge is required reading for many branches of analytic philosophy. The cosmopolitanism behind his political theory colors discourse about globalization and international relations. And some of his scientific contributions are even considered intellectual precursors to several ideas in contemporary cosmology.
Kant’s moral theory is organized around the idea that to act morally and to act in accordance with reason are one and the same. In virtue of being a rational agent (that is, in virtue of possessing practical reason, reason which is interested and goal-directed), one is obligated to follow the moral law that practical reason prescribes. To do otherwise is to act irrationally. Because Kant places his emphasis on the duty that comes with being a rational agent who is cognizant of the moral law, Kant’s theory is considered a form of deontology (deon- comes from the Greek for “duty” or “obligation”).
Like his theoretical philosophy, Kant’s practical philosophy is a priori, formal, and universal: the moral law is derived non-empirically from the very structure of practical reason itself (its form), and since all rational agents share the same practical reason, the moral law binds and obligates everyone equally. So what is this moral law that obligates all rational agents universally and a priori? The moral law is determined by what Kant refers to as the Categorical Imperative, which is the general principle that demands that one respect the humanity in oneself and in others, that one not make an exception for oneself when deliberating about how to act, and in general that one only act in accordance with rules that everyone could and should obey.
Although Kant insists that the moral law is equally binding for all rational agents, he also insists that the bindingness of the moral law is self-imposed: we autonomously prescribe the moral law to ourselves. Because Kant thinks that the kind of autonomy in question here is only possible under the presupposition of a transcendentally free basis of moral choice, the constraint that the moral law places on an agent is not only consistent with freedom of the will, it requires it. Hence, one of the most important aspects of Kant’s project is to show that we are justified in presupposing that our morally significant choices are grounded in a transcendental freedom (the very sort of freedom that Kant argued we could not prove through mere “theoretical” or “speculative” reason.
Kant begins his argument from the premise that a moral theory must be grounded in an account of what is unconditionally good. If something is merely conditionally good, that is, if its goodness depends on something else, then that other thing will either be merely conditionally good as well, in which case its goodness depends on yet another thing, or it will be unconditionally good. All goodness, then, must ultimately be traceable to something that is unconditionally good. There are many things that we typically think of as good but that are not truly unconditionally good. Beneficial resources such as money or power are often good, but since these things can be used for evil purposes, their goodness is conditional on the use to which they are put. Strength of character is generally a good thing, but again, if someone uses a strong character to successfully carry out evil plans, then the strong character is not good. Even happiness, according to Kant, is not unconditionally good. Although all humans universally desire to be happy, if someone is happy but does not deserve their happiness (because, for instance, their happiness results from stealing from the elderly), then it is not good for the person to be happy. Happiness is only good on the condition that the happiness is deserved.
The Categorical Imperative
If a good will is one that forms its intentions on the basis of correct principles of action, then we want to know what sort of principles these are. A principle that commands an action is called an “imperative.” Most imperatives are “hypothetical imperatives,” that is, they are commands that hold only if certain conditions are met. For instance: “if you want to be a successful shopkeeper, then cultivate a reputation for honesty.” Since hypothetical imperatives are conditioned on desires and the intended consequences of actions, they cannot serve as the principles that determine the intentions and volitions of an unconditionally good will. Instead, we require what Kant calls a “categorical imperative.” Where hypothetical imperatives take the form, “if y is desired/intended/sought, do x,” categorical imperatives simply take the form, “do x.” Since a categorical imperative is stripped of all reference to the consequences of an action, it is thereby stripped of all determinate content, and hence it is purely formal. And since it is unconditional, it holds universally. Hence a categorical imperative expresses only the very form of a universally binding law: “nothing is left but the conformity of actions as such with universal law” (4:402). To act morally, then, is to form one’s intentions on the basis of the very idea of a universal principle of action.