A broad classification of the sciences into physical, biological, and social corresponds with three levels of organization of matter and energy, and not levels only, but also quite distinct kinds of organization. The three are sharply increasing orders of complexity, and each includes the lower grades. Vital organization is more intricate than physical organization, and it is added to and does not replace physical organization, which is also fully involved in vital organization. Social organization retains and sums the complexities of both these and adds its own still greater complexities’.