It will be perceived that the rule of mutual service, when carried to its highest applications, presupposes the principle of individual differentiation, to which we have already attached so much weight. This principle is fundamental to fraternal as well as to paternal and filial duty. For precisely to the extent that brothers are distinctly individualized can they supplement each other and correlate their mutual services. One can not indeed overlook the patent fact that brothers who are unlike in nature frequently repel each other, and that in such cases the very closeness of the relation often becomes a source of extreme irritation, and even of positive agony. But, on the other hand, there is no surer sign of moral ripeness than the ability to enter into, to understand, to appreciate a nature totally unlike one's own, and thus to some extent to appropriate its excellences. The very fact, therefore, that we at first feel ourselves repelled should be taken as a hint that this natural repulsion is to be overcome. For every type of character needs its opposite to correct it. The idealist, for instance, needs the realist, if he would keep his balance. And our uncongenial brothers, precisely because they are at first uncongenial, if we will but remember that they are, after all, our brothers, and that it is our duty to come into harmonious relations with them, can best help us to this fine self-conquest, this true enrichment and enlargement of our moral being. A word may be added as a caution to parents and teachers. The way to create brotherly feeling among the young is to treat them impartially, to love them with an equal love. Those who love and are beloved by the same person are strongly induced to love one another. In the next place, when disputes arise, as is perhaps unavoidable, the parent or teacher should, as a rule, enter patiently into the cause and not cut off inquiry because the whole matter seems trivial. The subject matter of the dispute may be insignificant enough, but the satisfaction of the sense of justice of the young is of the greatest significance. When the sense of justice is outraged, be the cause never so trivial, a feeling of distrust against the parent is generated, and of incipient hatred against the brother who may have provoked the unjust decision.