These institutions which have thus been handed down, these habits of thought, points of view, mental attitudes and aptitudes, or what not, are therefore themselves a conservative factor.

This is the factor of social inertia, psychological inertia, conservatism.

Social structure changes, develops, adapts itself to an altered situation, only through a change in the habits of thought of the several classes of the community, or in the last analysis, through a change in the habits of thought of the individuals which make up the community.

The evolution of society is substantially a process of mental adaptation on the part of individuals under the stress of circumstances which will no longer tolerate habits of thought formed under and conforming to a different set of circumstances in the past.

For the immediate purpose it need not be a question of serious importance whether this adaptive process is a process of selection and survival of persistent ethnic types or a process of individual adaptation and an inheritance of acquired traits.
Social advance, especially as seen from the point of view of economic theory, consists in a continued progressive approach to an approximately exact "adjustment of inner relations to outer relations", but this adjustment is never definitively established, since the "outer relations" are subject to constant change as a consequence of the progressive change going on in the "inner relations." But the degree of approximation may be greater or less, depending on the facility with which an adjustment is made.