So far, we have shown that duties must be based on a categorical rather than a hypothetical imperative, and we have established the content of the one and only categorical imperative. We have yet to establish conclusively that the categorical imperative is a binding law for any rational being possessing a free will.
If there is some necessary law that compels rational beings to follow the categorical imperative, that law must be based on the concept of the "will" of a rational being. The "will" is the faculty that enables rational beings to choose what course of action to follow. Rational beings may pursue certain "ends" using appropriate "means." Ends that are based on physical needs or wants will always provide merely hypothetical imperatives. The categorical imperative, however, may be based only on something that is an "end in itself"-- that is, an end that is a means only to itself and not to some other need, desire, or purpose.
Rational beings are ends in themselves. In pursuing their objectives, rational beings must always view themselves not only as means to some purpose, but also as ends in themselves. They must also recognize that other rational beings are ends in themselves as well. Thus if we formulate the categorical imperative in terms of the will of a rational being, it would run as follows: act in such a way that you always treat other people not merely as means to some end, but also as ends in themselves.
The four examples of duty that were discussed earlier are consistent with this formulation of the law. When people commit suicide, they treat their own life as a mere means for escaping an upsetting situation. When people make false promises to repay debts, they treat the people they have borrowed from as mere means to their own financial gain. A view of humanity as an end in itself requires us to pursue the maximum fulfillment of humanity's potential, which means that we must cultivate our talents. Similarly, a view of humanity as an end in itself requires us to work towards maximum happiness for humanity, which means that we must take care for the welfare of others.
The principle that every rational being is an end in itself is universal and applies to all rational beings. It comes from reason, not from experience. Now, if rational beings are ends in themselves, and not means to some other end, then the will of a rational being must be thought of as the maker of universal law. Otherwise their actions would be governed by some interest and they would function as mere means to some purpose. When rational beings will something for the sake of duty alone, they must renounce all interests and motivations other than duty. Thus their obedience to the law cannot be based on any specific interest. Rather, they must understand themselves to be subjects as well as authors of the law, and they must recognize that the law requires unconditional obedience.
This notion of rational beings as simultaneous authors and subjects of universal law leads us to the idea of a perfect community in which all people follow the objective laws of reason and treat their fellows not merely as means to ends but also always as ends in themselves. This perfect community may be called the "kingdom of ends," meaning a legal community (kingdom) composed of ends in themselves which respects all its members as ends in themselves. Morality consists in adopting only those maxims and motives that are consistent with the establishment of a kingdom of ends.
The "dignity" of rational beings requires that they accept no law that they would not themselves have enacted. Commodities and products that serve physical needs and desires have "prices" in the market. By contrast, qualities that constitute people as ends in themselves have an intrinsic, absolute value--they have "dignity." The dignity of morality is the criterion for people to serve as lawmakers in the kingdom of ends.
Thus the principle of morality may be formulated in three distinct but interrelated ways: (1) in terms of the form of universality (act such that your maxim could become universal law); (2) in terms of their purpose or "end" (act such that all rational beings are respected as ends in themselves); and (3) in terms of a complete social system (act such that your maxim could be law in the kingdom of ends). An absolutely good will must never be in conflict with itself; its actions must have the intrinsic value of universal laws of reason. The purposes of an absolutely good will must never be relative only to certain ends, but must rather have the intrinsic value of ends that could be recognized by all rational beings. Consequently, the absolutely good will must choose its maxims as though it were a law-giver in the kingdom of ends--even though there is no guarantee that the contingencies of nature and the actions of other people will not prevent the establishment of such a kingdom.
When rational beings pursue morality and the kingdom of ends, they elevate themselves above the demands of nature and of their material circumstances. They thus establish the independence, or "autonomy," of their will. By contrast, when a person's goals are determined by something other than universal law, their will is "heteronomous"--it depends on external factors in determining its goals.
Other philosophical systems have made the mistake of advancing bases for morality that would in fact render the will heteronomous. "Empirical" principles--principles oriented toward some outcome in the physical world-- cannot be the basis of morality, because they are always heteronomous; even when the goal is personal happiness, concerns about particular outcomes or courses of events can never have the status of universal laws of nature. "Rational" principles like the will of God are likewise heteronomous because they do not come from pure concepts of reason; we have no notion of divine perfection other than that which we derive from our own moral concepts. Anytime someone does something in order to attain something else--whether that something else is happiness or perfection or the satisfaction of some physical need or desire--the person's will is determined by that something else; the will is heteronomous, and the maxim of the action makes sense only in particular circumstances, not as a universal law of nature.
We still have not shown that there is a law that compels us in practice to abide by the categorical imperative. We have shown, however, that our general presuppositions about morality (the idea that moral actions are undertaken for the sake of duty alone) are based on a notion of the autonomy of the will.
It may seem confusing that Kant precedes and follows his discussion of morality and the "will" with a disclaimer that he has not established that the categorical imperative has binding force for rational beings. Recall the provisional nature of Kant's argument in this book: it is only a "grounding" for the metaphysics of morals, not a full metaphysics of morals, let alone a complete analysis of "practical" (moral) reason and its role in our lives. Kant started off in Chapter 1 with the presupposition that people generally think of moral actions as actions performed for the sake of duty alone. He then developed an account of the "moral law" that may be based on this notion of duty and morality. In the first half of Chapter 2 he reformulated this moral law in terms of the categorical imperative. In the remainder of Chapter 2 he develops an account of the implications the moral law must have for the will of rational beings. Only in Chapter 3 will Kant explain that morality may be based on the concept of free will. As we will see, Kant qualifies even this statement by noting that the concept of free will cannot fully explain why we feel compelled to behave morally.
The fundamental idea that Kant introduces in the second half of Chapter 2 is that rational beings are "ends in themselves." When you settle on a course of action, Kant notes, you do not think of yourself as a means to some other purpose; you think of yourself as the purpose or "end" to which all your actions are directed. If you expect other people to accept your motives, you must respect the fact that other people also think of themselves as more than mere means to other goals. Thus your motives will lack universal validity unless you respect the fact that all rational beings have intrinsic worth, just as you do. The categorical imperative requires you to treat all your fellows as "ends in themselves"--that is, as objects of intrinsic value--and not as mere instruments for the attainment of your personal goals.
Kant's four examples of duty are no more successful in substantiating this idea than they were with the categorical imperative in the first half of the chapter. (Does failing to cultivate our talents really violate our notion that all people have intrinsic worth?) Nonetheless, his core insight fits fairly well with most people's basic sense of morality. In practice, Kant's notion of the "moral law" and the categorical imperative sounds a lot like the Biblical doctrine that we should treat other people as we would like them to treat us. Similarly, his notion of people as "ends in themselves" fits with the modern idea that all people possess a fundamental dignity. It is wrong to abuse people, or enslave them, or use them for selfish purposes, because doing so violates our sense that people are not physical objects that we may use as we see fit.
Kant's notion of a "kingdom of ends" also fits fairly well with modern ideas about politics. Though Kant is writing about morality, not politics, his description of the ideal community as one in which all people create their own laws is in essence a picture of democratic society. In practice, of course, societies must make laws by balancing different interests and viewpoints within a constitutional framework. In theory, however, democracies are based on Kant's notion that laws are valid if and only if they make sense to the people who must follow them.
Nevertheless, Kant's position is again vulnerable to the criticism that it is too abstract to be useful. Kant seems to think that reason is something static that people can use to develop universal laws and principles. In fact, different ideas make sense to people at different historical times and in different cultures. Kant seems to think that the notion that people are ends in themselves can provide clear moral guidance. In fact, this principle could be used in support of different viewpoints. (To pick just one controversial example, does abortion treat a potential baby as a mere means? Or would banning abortion treat women as mere means to the creation of babies?)
Kant's notion of "autonomy" is similarly suspect. Admittedly, Kant concedes that his notions of "autonomy" and of a "kingdom of ends" are ideal concepts that we cannot expect to encounter in real life. Still, we may want to ask whether it makes sense even to try to imagine a person making decisions without reference to any personal experience, cultural assumption, or material interest.