In the usage of David Ross, genuine obligations that may yet have to contend with others, and sometimes yield to them. An obligation to keep an appointment may yield to an obligation to take care of some emergency, in which case it was prima facie right to keep the appointment, but not right all things considered. Ross’s coinage is perhaps unfortunate, in suggesting a merely epistemological worry, as if on second appearance, or further thought, the obligation turned out to be illusory; whereas he himself believed that both conflicting obligations are real, even when one must give way to the other. A more modern usage prefers the title ‘pro tanto obligation’: an obligation inasmuch as there is this or that aspect of the situation, but again suspending the all-in verdict. In either event the difficulty for a deontological ethic is to explain how obligations are ranked, without bringing in overarching considerations of utility.