Here's a paper from my undergraduate days, which you might find mildly interesting in its outline (and critique) of both Kantian and Benthamite ethics. Personally, I don't really see the point in indulging in ethical system-building. We should just act so as to promote well-being, following our moral common sense in every situation we find ourselves in. When it isn't clear what the right thing to do is, well, we have to weigh our intuitions and make a choice. Kant, Bentham, Mill, Hume, Aristotle, and the hundreds of other theorists aren't particularly effective as guides, when you get right down to it. The Golden Rule is the last word of morality (and we should extend it, within reason, to the animal world as well).
Bentham and Kant present two diametrically opposed theories of morality. Bentham’s is consequentialist: it states that actions can be morally evaluated only on the basis of their consequences. (For example, lying is immoral if it leads to a person’s death.) Kant’s position is deontological: actions are intrinsically either right or wrong; their results do not matter. Since Kant’s ethics are based on his metaphysics, and Bentham does not even have a metaphysical system, the former theory is more complex than the latter. But that does not mean it is more correct; indeed, Kant’s ethics are more incorrect than Bentham’s—though Bentham’s are, in a sense, more superficial than Kant’s.
Bentham has both a psychological and a moral theory. The first claims that humans invariably desire to maximize pleasure and minimize pain; the second claims that actions are good only if they result in an augmentation of pleasure and are bad only if they increase pain. The moral theory is what concerns us in this paper. By this theory, the words “right” and “wrong” are meaningless without reference to utility. (For instance, what is right is what promotes the general welfare.) In regard to actions that affect society as a whole, an individual should forsake his own pleasure for the greater collective happiness.
Kant, on the other hand, does not think morality is even possible unless humans have free will. In other words, we cannot make use of practical reason, which is the branch of reason concerned with ethics, if we do not have the ability to govern our own actions. But this poses a problem: all of our experience leads us to believe there are causes determining how we think and act, so how can we be free and hence moral? Science teaches us that our thoughts and actions are caused by neurophysiological processes in our body; experience teaches us it is possible to feel virtually compelled to do something, to the extent of barely having free will in such moments (lust is an example); many philosophers teach us we are only deluding ourselves in believing in freedom. Kant responds to these objections by making a distinction between the thing in itself and the phenomenon. The first we have no access to; the second is everything we are commonly aware of, including facts that seem to refute free will. Now, according to Kant we are rational beings, and this means that in thinking or acting we cannot but assume ourselves to be free. (Philosophers may construct theories refuting free will, but it is impossible to act on this belief.) Kant discards the philosophical objections by relegating the debate between freedom and determinacy to the thing in itself, and hence to obscurity: theoretical reason cannot know anything about the thing in itself, so it cannot know if people are fundamentally (‘in themselves’) determined or free. This uncertainty is unavoidable, so we might as well continue to assume we are free—because, as was already stated, we cannot act as moral agents except on the supposition that we have free will.
It is as rational beings that we think we are free; hence morality, being based on freedom, must be grounded in reason. We cannot pursue ends in our moral actions, for this would subordinate us to causes in the phenomenal world (in this case desires, which are extrinsic to pure reason) and hence destroy our freedom, so we must act only for the sake of acting rationally. This means that we must find the ground of our moral actions in reason itself, which gives rise to the categorical imperative: “act only according to that maxim whereby you can at the same time will that it should become a universal law.” In other words, if the maxim of an action is contradictory with itself when universalized, it is wrong. Because the categorical imperative is the only moral law that pays no heed to consequences, it is the only one compatible with freedom.
On the basis of this theory Kant can criticize Bentham on the following grounds: (1) Bentham does not take into account the limits of theoretical reason (instead, he accepts the world as it appears to us and ignores the theoretical necessity of the thing in itself); (2) there can be no true freedom in Bentham’s system, since people are motivated by consequences—which implies that Bentham’s morality is not a morality at all. It is at most a convenient way of acting.
Bentham, on the other hand, criticizes Kant for the following reasons: (1) the categorical imperative, which requires people to act only for the sake of duty, is an impossible ideal (because people always act for empirical reasons); (2) obeying the categorical imperative may result in actions that do not promote the greatest happiness, so it is morally repugnant. Of course, this second objection presupposes rather than establishes Bentham’s own ethics, so it is of little value (even if we might agree with it). The first objection is an unproven psychological assertion. How do we know people cannot act solely on the recognition of duty? This claim seems impossible to prove, which is why Kant can resort to the argument that in cases where the only motive we are conscious of is the desire to act in accordance with duty, we can assume we are indeed doing so (for the truth lies in the realm of the thing in itself).
On the whole, if we accept Kant’s basic premises (e.g., the incapacity of theoretical reason to determine if we are truly free), it is difficult to refute his ethics. The reason is that he can always resort to the thing in itself: he can always say, “we don’t know that we are unfree”, “we don’t know we can’t act on duty alone”. However, this response deteriorates into dogmatism: it ends all discussion. Even if the thing in itself exists, falling back on inarguable claims is philosophically unacceptable. If nothing definite can be said about the thing in itself, it ought to be ignored and “phenomena” analyzed instead. Thus we should follow Hegel (and Nietzsche) in judging that Kantian ethics are empty and unreal.
Bentham’s ethics do not fare well either. His psychology, of course, is simplistic—it is a fact that people do not act solely to augment pleasure and avoid pain—but his hedonistic ethics are distasteful as well. First of all, it is impossible to make interpersonal comparisons of utility. We have no access to each other’s states of mind, so we have no idea how much pleasure other people experience. Secondly, Bentham does not provide a satisfactory argument as to why happiness should be pursued rather than pain, or why it should be pursued at all times. It is through pain, for instance, that we become stronger and that we acquire a greater appreciation of pleasure. Thirdly, pain and pleasure are sometimes indistinguishable from each other. For example, it is not always easy to decide whether one is happy or sad, or neither. Similarly, sadness can be gratifying, as when one enjoys it for its tranquilizing effect on the mind.
However, an important point is implied in Bentham’s system: no absolute, categorical morality exists. Anthropological investigations of morals lend support to the claim that morality, far from being required and determined by the nature of reason, is a relativistic human creation that is caused and influenced by various social factors. There is simply no good reason to believe that certain actions are inherently right or wrong, i.e. that morality is a priori, like logic and mathematics. Hence there is no good reason to believe in a deontological ethical system.
To conclude, this paper has argued that both Kant and Bentham are mistaken in their ethics. Kant, it seems, eventually has to become dogmatic, since his theory cannot effectively be argued against, and Bentham ignores certain facts about human existence. Lastly, I have argued that there is no ‘intrinsically right’ morality, which implies that consequentialism (when not hedonistically utilitarian) is the best theory by which to evaluate the moral status of actions.