It has been usual in expositions of economic theory to speak of capital as an array of "productive goods." What is immediately had in mind in this expression, as well as in the equivalent "capital goods," is the industrial equipment, primarily the mechanical appliances employed in the processes of industry. When the productive efficiency of these and of other subsidiary classes of capital goods is subjected to further analysis, it is not unusual to trace it back to the productive labor of the workmen, the labor of the individual workman being the ultimate productive factor in the commonly accepted systems of theory. The current theories of production, as also those of distribution, are drawn in individualistic terms, particularly when these theories are based on hedonistic premises, as they commonly are. Now, whatever may or may not be true for human conduct in some other bearing, in the economic respect man has never lived an isolated, self-sufficient life as an individual, either actually or potentially. Humanly speaking, such a thing is impossible. Neither an individual person nor a single household, nor a single line of descent, can maintain its life in isolation. Economically speaking, this is the characteristic trait of humanity that separates mankind from the other animals. The life-history of the race has been a life-history of human communities, of more or less considerable size, with more or less of group solidarity, and with more or less of cultural continuity over successive generations. The phenomena of human life occur only in this form.