It is clear, then, that the canon of productivity cannot be accepted to the exclusion of the principles of needs and efforts. It is not the only ethical rule of distribution. Is it a valid partial rule? Superior productivity is frequently due to larger effort and expense put forth in study and in other forms of industrial preparation. In such cases it demands superior rewards by the title of efforts and sacrifices. Where, however, the greater productivity is due merely to higher native qualities, physical or mental, the greater reward is not easily justified on purely ethical grounds. For it represents no personal responsibility, will-effort, or creativeness. Nevertheless, the great majority of the more fortunately endowed think that they are unfairly treated unless they are recompensed in proportion to their products. Sometimes this conviction is due to the fact that such men wrongly attribute their larger product to greater efforts. In very many cases, however, the possessors of superior productive power believe that they should be rewarded in proportion to their products, regardless of any other principle or factor. Probably the true explanation of this belief is to be found in man's innate laziness. While the prevalence of the conviction that superior productivity constitutes a just title to superior compensation, does create some kind of a presumption in favour of its correctness, it must be remembered that presumption is not proof. Weighing this presumption against the objective considerations on the opposite side of the argument, we take refuge in the conclusion that the ethical validity of the canon of comparative productivity can neither be certainly proved nor certainly disproved.