No matter how it is viewed, as a plausible version of anti-utilitarianism or of non-consequentialist, or even as a plausible version of deontology, the theory of prima facie duties certainly makes W. D. Ross one of the most important moral philosopher of the twentieth-century. By outlining his pluralistic deontology, this paper attempts to argue for a positive answer to the question of whether Ross’s theory can offer a solution to the issue of conflicting duties. If such a solution is convincing, as I believe it is, it would indicate the possibility to justify within the deontological framework, i.e., without committing to the principle of good-maximizing, those “hard cases” where people should break a promise or other (prima faci...