Excess of fertility is then the cause of man's further evolution. And the obvious corollary is that man's further evolution itself necessitates a decline in his fertility. The further progress of civilisation will be accompanied by an enhanced cost of individuation: whether it be in greater growth of the organs which subserve self-maintenance, in their added complexity of structure, or in their higher activity, the abstraction of the required material, implies a diminished reserve of materials for race maintenance. This greater emotional and intellectual development does not necessarily mean a mentally laborious life--for, as the goal becomes organic, it will become spontaneous and pleasurable. The necessary antagonism of individuation and genesis not only fulfils the _a priori_ law of maintenance of the race from the monad up to man, but insures final attainment of the highest form of this maintenance--a form in which the amount of life shall be the greatest possible and the births and deaths as few as possible. From the beginning pressure of population has been the proximate cause of progress. After having duly stocked the globe with inhabitants; raised all its habitable parts into the highest state of culture; brought all processes for the satisfaction of human wants to perfection; developed the intellect into complete competency for its work, and the feelings into complete fitness for social life; the pressure of population as it gradually finished its work, must gradually bring itself to an end. Changes, numerical, social, organic, must by their mutual influences work unceasingly towards a state of harmony--a state in which each of the factors is just equal to its work. And this highest conceivable result must be wrought out by the same universal process which the simplest inorganic action illustrates. Principles of Sociology "Principles of Sociology" was published in four parts from 1876 to 1880. It forms part of a connected series. In "First Principles" inorganic evolution--that of the stars and of the solar system--was outlined; organic evolution was dealt with in "Principles of Biology;" and in the present treatise, "Principles of Sociology," we approach super-organic evolution, and are introduced to the science of society under its Comtist title "Sociology." Super-organic evolution may be marked off from, organic by taking it to include all those processes and products which imply the co-ordinated action of many individuals. Commencing with the development of the family, sociology has next to describe and explain the rise and development of political organisation; the evolution of the ecclesiastical structures and functions; the control embodied in ceremonial observances; and the relations between the regulative and operative divisions of every society. _I.--Domestic_