Doing Our Duty

by Mortimer J. Adler, Ph.D.

Dear Dr. Adler,

Duty is the highest virtue of the soldier. But there are also political, moral, and Religious duties, as we are constantly reminded. What do the philosophers have to say about the nature of duty and its role in human conduct?

J. D.


Dear J. D.,

There is perhaps no more fundamental issue in moral philosophy than that between the ethics of duty and the ethics of pleasure or happiness. According to the morality of duty, every act is to be judged for its obedience or disobedience to law, and the basic moral distinction is between right and wrong. But where pleasure or happiness is central, the basic distinction is between good and evil, and desire rather than law sets the standard of appraisal. Of course, any ethics of duty has to take some account of happiness, just as any ethics of happiness and pleasure has something to say about duty. But there are great differences in the role which is assigned to duty.

At one extreme there is the position which totally excludes the concept of duty. This attitude more than any other characterizes the Epicureanism of Lucretius.

In Aristotle’s ethics of happiness, duty is not entirely excluded, but neither is it given any independent significance. It is merely an aspect of the virtue of justice, and amounts to no more than the just man’s acknowledgment of the debt he owes to others: or his recognition that he is under some obligation to avoid injuring other men and to serve the common good.

For Plato, too, the virtue of justice underlies duty or obligation. But for him justice, though only one of the virtues, is inseparable from the other three — temperance, courage, and wisdom. It is almost indifferent, therefore, whether one attributes moral obligation to our sense of justice or to virtue in general.

At the other extreme there is the position which identifies the sense of duty with the moral sense. In the Stoicism of Marcus Aurelius and Epictetus, to act rightly is to do one’s duty and to set aside all contrary desires.

Kant’s much more elaborate moral philosophy presents the same fundamental teaching. Nothing can be conceived as “good, without qualification,” except a “good will.” Happiness is not a good without qualification. It is “a rational being’s consciousness of the pleasantness of life uninterruptedly accompanying his whole existence,” and its basis is “the principle of self-love.” An ethics based on happiness and one based on pleasure both commit the same mistake. Both “undermine morality and destroy its sublimity, since they put the motives to virtue and vice in the same class, and only teach us to make a better calculation.” Both admit desire as a moral criterion of good and evil. Both measure the moral act by reference to the end it serves.

For Kant, “an action done from duty derives its moral worth, not from the purpose which is to be attained by it, but from the maxim by which it is determined…” And so he goes on to say that “duty is the necessity of acting from respect for the law.” From this he argues that duty, and consequently all moral action, must be done because it is right, because the law commands it, and for no other reason.

“An action done from duty,” Kant writes, “must wholly exclude the influence of inclination, and with it every object of the will, so that nothing remains which can determine the will except objectively the law, and subjectively pure respect for this practical law…” The law, which is the source of duty and of all moral action, is Kant’s famous “categorical imperative.” According to its decree, Kant declares, “I am never to act otherwise than so that I could also will that my maxim should become a universal law.” By obeying the categorical imperative, we can do our duty and rest assured that our will is morally good.

For Kant, therefore, duty is objective. It consists in following the commands of the categorical imperative, independently of subjective inclinations, desires, and needs. In doing our duty, we follow the voice of reason alone.


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