  An example of a preemptive duty is the case of a promissory obligation. If I have agreed to do something for you and I suddenly see some pleasurable alternative to fulfilling my obligation, most people would think that I ought to exclude the consideration of pleasure altogether from my deliberations even though the pleasure would be a consideration had I made no promise. It is simply not something that I can legitimately weigh in the balance against the promissory obligation. So if an authority issues a command and the duty to obey is a preemptive duty, then the subject does not weigh the other duties that might otherwise apply to him in the balance with the preemptive duty. The preemptive duty simply excludes the other duties. By contrast, if a duty is not preemptive, then when it comes time to comply with it, one must balance it with other duties that weigh for and against acting in accord with the duty.