While the evolution of such superior functions involves a corresponding differentiation, and therefore a _division_ and _separation_ of the superior functions within the social structure, the necessity for _communication_ and for _mutual support_ results in an _approximation_ of the individuals and the groups. In every society, therefore, the centrifugal and the centripetal forces work simultaneously in co-operation and in opposition to one another. While the extreme specialization on the one hand seems to make for the best individual functioning, on the other hand it renders the entire collective structure much more dependent, and therefore much more subject to injury, as is shown by the example of the queen bee, whose departure threatens the existence of the entire hive. Thus a medium degree of differentiation will as a general rule produce the most permanent social structure. =59. Language and Intercourse.= The essential value of the social organization resides in the fact that the work of the individual, in so far as it is adapted to it, accrues to the benefit of the collective whole. For this it is absolutely essential that the members of the collectivity should be able to _have intercourse_ with one another in order that every part of the general activity may be communicated to the others. This intercourse is obtained through language in the most general sense. We have already learned that the essence of language consists in the co-ordination of concept to sign. The social application of language demands that the signs co-ordinated to the concepts in use should be the same for all the members of the social organization. Only in this way can the members make themselves mutually understood. But intelligible means of communication and division of labor impart to the social knowledge that is set down in writing a kind of independent existence. Many centuries ago the possibility ceased for one person to store in his memory the entire stock of human knowledge. Nowadays we have men who are versed only in single parts of separate sciences, and the aggregate knowledge appears at first to be a unity existing only in thought. But because this knowledge is set down in signs which endure far beyond the life of the individual and at the appropriate moment can unfold its entire power even after a long period of inactivity, it has acquired an existence of a social character independent of the individual. For although it survives the individual, it cannot survive the death of human society.