It is plain, as MacCurdy has well pointed out[10], that men entering the Army, and particularly on approaching the battle-field, have to undergo a very considerable readjustment of their previous attitudes of mind and standards of conduct, a readjustment which is much greater in the case of some men than in that of others, and also one which some men find it much more easy to accomplish satisfactorily than do others. The man’s previous standards of general morality, of cleanliness and æsthetic feeling, and of his relation to his fellow-man, have all to undergo a very considerable alteration. In all directions he has to do things that previously were repugnant to his strongest ideals. These ideals are ascribed by some—e.g., Trotter[11], and, following him, MacCurdy—to the operation of the herd instinct, in other words to the influence of the social _milieu_ in which he may happen to have been brought up. I think personally that behind this influence there are still deeper factors at work of a more individual order, derived essentially from hereditary tendencies and the earliest relation of the child to its parents. However this may be, it is certain that every one has such ideals, though he may not describe them under this name, and that in the course of development he insensibly builds up a series of standards of which his ego approves—and which I therefore propose to refer to by Freud’s term of the “ego ideal”—together with a contrasting series of which his ego disapproves.