Immanuel Kant was a German philosopher who was part of the enlightenment in the late sixteen hundreds. Kant proposed many ideas during his life time, but one of the most argued is the categorical imperative. The categorical imperative states; act only on that maxim which can become a universal law. When given the argument, "I will not pay my debts whenever it's in my interest to do so". This maxim isn't able to be a categorical imperative because it cannot be a universal law. We ought to pay or debts whether it is in our best interest or not. .
Kant's moral theory is deontological which means that actions are morally right in virtue of motives, which must derive more from duty other than from inclination. It is our duty to pay debts. We ought to do it because it has the ability to be a universal law. Ought does not imply is, but it does imply can. When we tell someone they ought to pay their debts it is not going to make them do it, however it does imply that you can do that task. This ties into psychological and ethical egoism. Ethical egoism is the position that moral agents ought to do what is in their own self-interest. It differs from psychological egoism, which claims that people can only act in their self-interest. Ethical egoism holds that actions whose consequences will benefit the doer can be considered ethical. Kant would argue against both of these ideas because he believes that what is morally good can only be good for all people regardless of their interests and or desires. .
Alternatively there is an idea that goes against Kant's argument entitled ethical relativism. The University of Santa Clara describes ethical relativism as, "The theory that holds that morality is relative to the norms of one's culture. That is, whether an action is right or wrong depends on the moral norms of the society in which it is practiced. The same action may be morally right in one society but be morally wrong in another.