g is alike the incentive to a higher
education of children, and to a more intense and long-continued
application in adults. Nothing but necessity could make men submit to
this discipline; and nothing but this discipline could produce a
continued progression.

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,