They show that states of surplus and deficit affect not only moral traits but also create degeneration and retardation. Psychology, however, has added a clearly defined cause of non-development which had escaped notice. The growth of an organ depends partly on the direction given to growth by the unit characters of the germ-cell and partly to the use to which it is put. Even if the forces of the germ-cell are normal no organ will fully develop without constant exercise. Regression in an organ will take place if the stimuli to exercise are absent. These stimuli lie not in the organ, but in the brain cells. Mental activity may fail from three causes. Psychic traits may be inactive through degeneration: they may not develop because of retardation: or the environment may lack the elements that arouse their activity. In each of these cases the trouble lies in objective facts mainly if not solely of an economic nature. Regressions do not differ in their origin from degenerations and retardations. They all arise from defects in the environment and thus do not indicate changes in the unit-characters of the germ-cell.
A study of man should begin with his social nature and with the degenerate forces at work within him. These two problems run into each other because it is man's social nature that has stopped elimination. Society uses its nurture to keep the weak alive and hence improved conditions means not progress but degeneration. A second difference between men and animals arises out of the social classes which differences in income create. The poor are in this way subject to exploitation and held in the grip of want. Dr. Woods says men have choices and can escape their environment. This is in a degree true of the higher income levels but not of the poor. Their fate is as definite and as objective as that of any lower animal. Along with poverty goes physical retardation, and the two combined are responsible for the mass of traits associated with the poor. A full maturity depends on the stimuli that evoke activity and hence promote growth. These stimuli are psychic traits made active in men by contact with the economic environment. This means that wealth is needed to place around each family the proper objects to excite interest: without them the psychic powers are dormant and the physical are regressive.
The environment of a man is determined not by his geographical habitat, but by his income. The various income levels of society create as marked differences in men as differences in latitude do in animals. The influence of environment on man is therefore not less but different from the same influence on animals. All virtues and defects in men are environmental. The virtues are social; the defects are degenerations, retardations and regressions. Most observable traits come under these heads. They change with the environment and not with the germ cell. Only those changes that are really progressive can be