complexity. The phenomena and forces of each science appear in all the sciences which succeed, but not in those which precede, it in the scale. Each science is thus engaged in the study of a new set of forces and phenomena. The order of the sciences here stated is, therefore, the order of increasing complexity and diminishing generality.
The foregoing classifications of the evolutionary process, forces, phenomena and sciences may be resumed in the following table:
| Evolution | Forces | Phenomena | Sciences |
| Cosmic | Atomic | Chemical | Chemistry |
| Molecular | Physics | ||
| Molar | Physical | ||
| Organic | Biotic | Biological | Biology |
| Psychic | Psychological | Psychology | |
| Social | Social | Sociological | Sociology |
It is not necessary to contend or assert that the forces of the various fields of phenomena, and the consequent extent of the respective sciences are, or ever can be, as sharply defined as the foregoing discussion might seem to indicate. The possible overlapping of the fields of phenomena and the corresponding sciences should be indicated in the table by an arrangement of braces connecting them.
Chemistry, physics, biology, psychology and sociology are, then, the five great divisions in a comprehensive classification of the sciences. They are the five great stems or branches out of which all the other and more special sciences necessarily develop. There is no true science which may not be subsumed under one or the other of these general sciences.
Let us now compare the foregoing classification of the sciences with others, particularly those of Comte and Spencer. Comte's well-known "hierarchy" of the sciences includes the following: mathematics, astronomy, physics, chemistry, biology and sociology. Spencer includes in the concrete sciences astronomy, geology, biology, psychology, sociology and ethics. As already observed, Comte indicated a belief that mathematics is not a true science. It should also be noticed that he gave to biology a wider meaning than is ordinarily ascribed to it. He included what he called "transcendental biology," by which we may understand cerebral biology or psychology. He also, in his later writings, made ethics the final term of the series. His classification needs to be rearranged before a comparison is made. This rearrangement has been made by Professor Ward in a comparison of the classifications of Comte and Spencer. For convenience in comparison, we shall place the classification of Comte, Spencer and the one proposed in parallel columns:
