Each successive move in advance, every new wrinkle of novelty, improvement, invention, adaptation, every further detail of workmanlike innovation, is of course made by individuals and comes out of individual experience and initiative, since the generations of mankind live only in individuals. But each move so made is necessarily made by individuals immersed in the community and exposed to the discipline of group life as it runs in the community, since all life is necessarily group life. The phenomena of human life occur only in this form. It is only as an outcome of this discipline that comes with the routine of group life, and by help of the commonplace knowledge diffused through the community, that any of its members are enabled to make any new move that may in this way be traceable to their individual initiative. Any new technological departure necessarily takes its rise in the workmanlike endeavours of given individuals, but it can do so only by force of their familiarity with the body of knowledge which the group already has in hand. A new departure is always and necessarily an improvement on or alteration in that state of the industrial arts that is already in the keeping of the group at large; and every expedient or innovation, great or small, that so is hit upon goes into effect by going into the common stock of technological resources carried by the group. It can take effect only in this way. Such group solidarity is a necessity of the case, both for the acquirement and use of this immaterial equipment that is spoken of as the state of the industrial arts and for its custody and transmission from generation to generation.