For both Kant and Hume, it is wrong to make a promise intending not to keep it. If one gives one's word to do something, this creates an obligation to be fulfilled. The actor must keep the promise, which means that he or she must act because of something they have done in the past; namely, making a promise.
For Kant, ethical behavior creates and follows a maxim, and a maxim is a subjective principle of volition, a principle on which the agent acts to determine his or her decisions. Kant's statement is another way of saying that the action will have moral worth because it will have been performed for the sake of duty because it is based on the maxim of obeying universal law as such. This last statement by Kant is a way of creating a practical means of action for the moral life. Reverence for law is the rationale for the maxim of acting in accordance with the law as such, and universality is the characteristic mark of the law. Kant explains this through an example involving a man in distress who can escape only by making a promise he has no intention of keeping. To lie in this manner, if universalized, would mean that everyone could lie if they find themselves in a difficult situation and can escape in no other way. This is not allowed because it would mean that the individual was willing a lie to become a universal law. This sort of maxim has to be rejected because it cannot enter into universal law. The subjective principles of volition by which we make decisions can make good decisions or bad decisions, and if that will is to be good, the decisions we make should become universal laws. If they cannot, they fail the test.
David Hume considers what elements exist in human nature that decide how we behave and how we should behave. For Hume, how we behave may depend on the stability of our social environment and on the development of a stable social environment. In a more primitive state, it would be expected ...