This chapter deals with the era dominated by social organism theory. In sociology, social organism theory is an approach that analyzes society by comparing it to a living organism where all parts are organically connected and function together. The massive influx of sociology into Japan occurred around 1900, near the end of the Meiji era. Among the various sociological theories introduced during this period, A. Comte’s sociology rose to prominence, replacing Spencer, who had dominated the previous era. A distinctive characteristic of Japanese sociology appears in the fact that, contrary to the chronological order of Western sociological history, Spencer’s evolutionary sociology became popular first in Japan, followed by the flourishing of Comte’s social organism theory. Comte rejected J.J. Rousseau’s social contract theory and instead introduced an organismic perspective modeled after biology. Just as biology analyzes the body’s structure and functions, Comte divided sociology into social statics (analysis of structure and order) and dynamics (study of development and progress) (H. Spencer also advocated a theory of social evolution where society, as an organism, differentiates and develops from simple to complex forms, similar to biological organisms. In this sense, Spencer was also a supporter of social organism theory.). In Japan, Tongo Takebe became the leading proponent of this organismic sociology.