The definition of inclination has varying definitions in philosophy. Aristotle "holds it to be the mark of a good person to take pleasure in moral action," or what one wants to do. Immanuel Kant made a study of whether inclination is of the highest moral worth, and objected to Aristotle's analysis, reasoning that "it is the person who acts from the motive of duty in the teeth of contrary inclination who shows an especially high degree of moral worth."
The Shopkeeper
Kant posits the example of a shopkeeper who continually charges fair prices to customers in order to build good will and repeat business. If the shopkeeper continued that practice due to a mere inclination rather than sense of duty, though the shopkeeper's keeping the prices fair may conform with duty it has "no true moral worth." If instead the shopkeeper kept the prices fair solely out a duty to justice then he is acting simply from that duty. And in that case, in so doing Kant argues that the act now has "genuine moral worth." But changing the facts of the example might lead to an altogether different conclusion. If instead the shopkeeper is nearly bankrupt and desperately needs money to feed his family, and still the shopkeeper keeps the prices fair less out of a sense of duty but rather a sense of pride, then some may argue that it is more impressive to stay fair under those circumstances.
Criticism
Kant argues that acting out of pure duty has the highest value, in that the visitor is doing the right thing for the right reason, because it is the right thing to do. It is not always clear whether inclination is morally more worthy than duty, or vice versa. For example, if following one's moral duty to always tell the truth has the highest value, then telling the truth where it results in the murder of that person may show that following pure duty may not have the highest moral value. But many criticisms of Kant do not take into account that he did not preclude other acts from having moral worth, instead Kant is said to have only valued acting from pure duty as having "true" or "authentic" moral worth. Philosophers tend to disagree on whether operating solely out of duty is always the most morally worthy thing to do, rather than operating via inclination.
One famous example illustrates the difference between inclination and duty while illustrating a criticism of it, as given by Michael Stocker in his paper The Schizophrenia of Modern Ethical Theories. The visitor could be seen as lacking in moral merit. In other words, which scenario has more moral worth: one in which the friend goes to the hospital out of a cold sense of duty instead of wanting to do it ? Kant might argue that the former has the "true" or "authentic" moral worthiness where Stocker argues acting purely out of duty in his example is morally inauthentic.
