MENTAL SYSTEMS 49
process is not only not checked but is proceeding at an ac celerating rate. It seems to be due to the operation of fundamental laws of being ; and, while it is true that the ap pearance of new forms of activity sometimes leads to the discontinuance of old forms, each new form, after it appears, leads most likely to the introduction of several others. Thus the total number of differentiated forms of activity is constantly on the increase. All men are becoming special ized. A glance backward to earlier social conditions is sufficient to confirm the statement that this specialization is a rapidly increasing process. If we recall how in early society, before the beginning of the exchange of goods be tween groups, all the customary forms of activity were carried on within one small circle, without any clear division of labour except between the sexes ; if we further consider how, with the expansion of the groups and the establishment of relations between neighbouring groups, the differentia tion of occupations within each group proceeded ; and if we follow this process until it issues in the almost infinite maze of differentiated activity of our present-day life, we shall perceive that we are now stationed where the past develop ment, like a broadening Amazon, expands into an era of com plicated specialization of truly oceanic proportions. There are some seventeen thousand different occupational desig nations in current use, though many of them indicate forms of activity so nearly alike that our Census Bureau finds that there are only about ten thousand which are of service in its enumeration. By far the greater number of these are of comparatively recent origin. Who can tell to what extent this process of specialization is to go, or how profoundly it is to modify the mental development of the people?
But the differentiation of occupations, though very im portant, is by no means the only influence at work produc ing variations and divergences among the mental systems of men. Native organic differences are also important causes of these divergences. Human beings do not inherit a com pletely and rigidly organized nervous constitution, but each
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