The backwardness of social knowledge is marked in its division into independent and insulated branches of learning. Anthropology, history, sociology, morals, economics, political science, go their own ways without constant and systematized fruitful interaction. Only in appearance is there a similar division in physical knowledge. There is continuous cross-fertilization between astronomy, physics, chemistry and the biological sciences. Discoveries and improved methods are so recorded and organized that constant exchange and intercommunication take place. The isolation of the humane subjects from one another is connected with their aloofness from physical knowledge. The mind still draws a sharp separation between the world in which man lives and the life of man in and by that world, a cleft reflected in the separation of man himself into a body and a mind, which, it is currently supposed, can be known and dealt with apart. That for the past three centuries energy should have gone chiefly into physical inquiry, beginning with the things most remote from man such as heavenly bodies, was to have been expected. The history of the physical sciences reveals a certain order in which they developed. Mathematical tools had to be employed before a new astronomy could be constructed. Physics advanced when ideas worked out in connection with the solar system were used to describe happenings on the earth. Chemistry waited on the advance of physics; the sciences of living things required the material and methods of physics and chemistry in order to make headway. Human psychology ceased to be chiefly speculative opinion only when biological and physiological conclusions were available. All this is natural and seemingly inevitable. Things which had the most outlying and indirect connection with human interests had to be mastered in some degree before inquiries could competently converge upon man himself.