Various explanations that strike deeper than surface observation have been proposed as solutions for this cardinal problem of the social one and the social many; of the relation of society to the individual. Society has been described as a tool, an instrument, as it were, an extension of the individual organism. The argument runs something like this: The human hand, though indeed a part of the physical organism, may be regarded as an instrument of the body as a whole. If, as by accident it be lost, it is conceivable that a mechanical hand might be substituted for it, which, though not a part of the body, would function for all practical purposes as a hand of flesh and blood. A hoe may be regarded as a highly specialized hand, so also logically, if less figuratively, a plow. So the hand of another person if it does your bidding may be regarded as your instrument, your hand. Language is witness to the fact that employers speak of "the hands" which they "work." Social institutions may likewise be thought of as tools of individuals for accomplishing their purposes. Logically, therefore, society, either as a sum of institutions or as a collection of persons, may be conceived of as a sum total of instrumentalities, extensions of the functions of the human organism which enable individuals to carry on life-activities. From this standpoint society is an immense co-operative concern of mutual services. This latter is an aspect of society which economists have sought to isolate and study. From this point of view the relations of individuals are conceived as purely external to one another, like that of the plants in a plant community. Co-operation, so far as it exists, is competitive and "free." In contrast with the view of society which regards social institutions and the community itself as the mere instruments and tools of the individuals who compose it, is that which conceives society as resting upon biological adaptations, that is to say upon instincts, gregariousness, for example, imitation, or like-mindedness. The classic examples of societies based on instinct are the social insects, the well-known bee and the celebrated ant. In human society the family, with its characteristic differences and interdependences of the sexes and the age groups, husband and wife, children and parents, most nearly realizes this description of society. In so far as the organization of society is predetermined by inherited or constitutional differences, as is the case pre-eminently in the so-called animal societies, competition ceases and the relations of its component individuals become, so to speak, internal, and a permanent part of the structure of the group.