Kant’s emphasis is on the universality of the maxim of a man’s action. Can he, for instance, mislead the person who is to loan him money by claiming that he has or will have sufficient funds in the future to pay him back?

Kant firmly answers in the negative, for to universalize this principle would be to render it self-contradictory. Note that while Kant states that taking the loan in this instance would of course be to one’s own personal advantage, we must instead ask whether it is right. It is advantageous, but is it good? This question later finds itself expressed in a slightly different manner by G.E. Moore in the open question argument.

For Kant, it is not enough that the universalization of a maxim leads to terrible consequences. Indeed, for him it is totally irrelevant, and he takes great pride in adopting such a position. Like Plato, he is suspicious of material objects and downright hostile to philosophical anthropology masquerading as a complete system of morality. While anthropology is taken somewhat into account, Kant says that it must first and always be preceded by a proper metaphysics of morals. But back to consequences: in order for the universalization maxim to fail, it must fail based on formal considerations only, or else it will lose its semblance of mathematical precision and certainty. Therefore, Kant claims that the flaw inherent in the loan example is actually one that is self-contradictory—it would make the very institution of ‘promising’ impossible. 

Here Kant brings in another part of the Categorical Imperative. If, for some reason the man cannot see that his false promise is self-contradictory upon universalization, he should at least be able to see that this false promise treats the originator of the loan as merely a means to an end, rather than an end in himself. This is a formalization of the principle delivered by Jesus: ‘Do unto others as you would have them do unto you’. Arguably, however, Kant goes much further by developing his entire ethical system around rational autonomy, a concept not without its difficulties. Kant was working within a mechanistic philosophical background, in which he attempts to solve the problem of the dichotomy between rationalism and empiricism. He had Scholastic metaphysics on the one hand, and Hume’s Epicurean materialism on the other, in addition to Newton’s ground-breaking work in physics. His task, then, was to reconcile the two by accounting for abstract, a priori knowledge, since his account of morals absolutely required it—no a priori knowledge, then no ethics because the only alternative foundation would be empiricism. Although Hume awoke Kant fromhis dogmatic slumbers, he was hardly ready to adopt such a staunch empiricism. Borrowing Hume’s distinction between relations of ideas and the facts of experience, Kant developed the notion of the analytic and the synthetic.

Analytic knowledge was knowledge that was necessarily true; it was achieved by examining the concepts and their relations with one another. Hence, it’s not necessary to get off one’s armchair and explore the world to conclude that the statement: ‘All unmarried men are bachelors’—is not only true, but necessarily so. It would be ludicrous to suggest that we could empirically discover a counterexample. Mathematics is in a similar category, although since it speaks directly to the empirical world, Kant calls this synthetic a priori knowledge. This is the most fascinating of his claims. There is nothing significant about forming tautologies in one’s own mind. They are true, yes, but trivially so. But this is a different claim: synthetic a priori knowledge is that which is created purely by abstract reasoning and speculation, but is nevertheless necessarily true. It sounds similar to Plato’s theory of the forms, but has a little bit less of an excess in the department of ontology. So when talking about theorems of triangles, one really means to say something about the real world, even though one comes to this knowledge by pure speculation, according to Kant.

As it is in mathematics, so it is in ethics. Treating a person merely as a means to an end is wrong because it violates dignity. What are we to make of this ethereal idea? Kant conceives of dignity as rooted in rationality and autonomy, together. The reason why we as subjects have the property of dignity, while an object does not, is because an object does not have freedom of the will. This is where Kant develops the ought/can distinction. To have a duty to do something, you have to be able to do it. I do not, for instance, have a duty to obey the law of gravity, for it is nothing I can either do or not do. It just is. In the same way, since an object has no will, applying moral categories to it would be futile.

The second part of the equation is rationality. One must be autonomous in the sense that one’s moral choices are not influenced by external causes or circumstances, but rather by internal contemplation. Furthermore, to add to autonomy, one must do one’s duty for the sake of being moral; that is all that is permitted if the action is to be moral. Hypothetical imperatives do not count. While it certainly is a nice thing to volunteer in a soup kitchen, if you mean it only for self-interested reasons, then it becomes properly amoral, that is, devoid of any moral content, whatsoever. But with rationality, one must be essentially rational and for the most part be in active operation of reason. And Kant divides the two because he considers coma patients to be essentially rational, but not rationally operative, and so this is where the concept of dignity encounters some potential problems.

Kant’s position on morality closely resembles that of Plato, but he also imparts teleology into his equation in claiming that nature does nothing in van; it is purposive. However, Kant differs from Aristotle strongly because Kant believes that character plays no role in determining morality. It is far too arbitrary a metric to be considered. Rational autonomy cannot be encumbered by character, race, gender, or physical appearance.