Legal Obligation does not concern itself with disposition, which does not matter to it so long as the action is performed. But in the case of ethical Obligation, the impulsive ground must be an inner one; the action must be done because it is proper that it should be done. We must, for instance, pay our debts not because we can be compelled but because it is right that we should.
(Immanuel Kant, Lectures on Ethics, trans. Louis Infield, The Library of Religion and Culture, ed. Benjamin Nelson [New York: Harper & Row, 1963 (first published in 1930)], 48)
