Kant claimed that all duty is absolute. He couldn’t conceive of a situation where universal obligations would fundamentally conflict. Ross, on the other hand, regarded duties as conditional. He could imagine times of tragic moral choice when to fulfill one obligation on his list above is to violate another. In those cases people should act so as to fulfill their higher obligation. The six duties are ranked in order of importance. The ones higher up are "most stringent" and take precedence over those lower down.