Thus much concerning the filial relations. We pass on to speak of the fraternal duties; the duties of brothers to brothers and sisters to sisters; of brothers to sisters and conversely; of older to younger brothers and sisters and conversely. The fraternal duties are founded upon the respect which equals owe to equals. The brotherly relation is of immense pedagogic value, inasmuch as it educates us for the fulfillment later on of our duties toward all equals, be they kinsmen or not. As between brothers, the respect of each for the rights of the other is made comparatively easy by natural inclination. The tie of blood, close and constant association in the same house, common experience of domestic pleasures and sorrows--all this tends to link the hearts of the brothers together, and thus the first lessons in one of the hardest duties are given by Love, the gentlest of school-masters. But the word equality must not be misconceived. Equality is not to be taken in its mathematical sense. One brother is gifted and may eventually rise to wealth and fame, another is Nature's step-child; one sister is beautiful, another the opposite. If the idea of equality be pressed to a literal meaning, it is sure to give rise to ugly feelings in the hearts of the less fortunate. How, then, shall we define equality in the moral sense? A superior, as we have seen, renders services which the inferior can not adequately return. Equals are those who are so far on the same level as to be capable of rendering mutual services, alike in importance, though not necessarily the same in kind. Equals are correlative to one another. The services of each are complementary to those of the other. The idea of _mutual service_, therefore, is characteristic of the relation of brothers, and the rule of duty may be formulated simply, Serve one another. From this follow all the minor commands and prohibitions which are usually impressed upon children,[18] and also the far loftier counsels which apply only to adults.