to be sound, we must regard the personality of the adult as the resultant of three groups of forces to which the mind from infancy onwards is subject; first the egoistic instincts of the individual pressing for gratification and possessing the intense mental energy characteristic of instinctive processes, secondly the specific sensitiveness to environmental influences which the mind as that of a gregarious animal necessarily possesses, a quality capable of endowing outside influences with the energy of instinct and, thirdly the environmental influences which act upon the growing mind and are also essentially determined in their intensity and uniformity by instinctive mechanisms.
The work of Freud has been directed mainly to the elucidation of the processes included in the first group—that is to say, to the study of the primarily egoistic impulses and the modifications {88} they develop under restraint. He has worked out, in fact, a veritable embryology of the mind.
The embryology of the body is to those who have had no biological training far from being a gratifying subject of contemplation. The stages through which the