Any comprehensive survey of modern civilized life cannot fail to yield abundant instances of the disproportionate influence in the conduct of affairs which has been acquired by mere age. When we remember how little in actual practice man proves himself capable of the use of reason, how very little {87} he actually does profit by experience though the phrase is always in his mouth, it must be obvious that there is some strong psychological reason for the predominance of age, something which must be determinative in its favour quite apart from its merits and capacity when competing with youth. The “monstrous regiment” of old men—and to the biologist it is almost as “monstrous” as the regiment of Mary Stuart was to poor indignant Knox—extends into every branch of man’s activity. We prefer old judges, old lawyers, old politicians, old doctors, old generals, and when their functions involve any immediacy of cause and effect and are not merely concerned with abstractions, we contentedly pay the price which the inelasticity of these ripe minds is sometimes apt to incur. IV If the propositions already laid down prove 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.