As every student of genetic psychology knows, this gradual building up is never performed smoothly, but always after a number of both conscious and unconscious internal conflicts between the conscious ego on the one side and various impulses and desires on the other, after a series of partial renunciations and compromises. Further, it is exceptional for the whole result to be satisfactory; there always remain certain fields—more especially in the realm of sex—where the resolution of the conflict is an imperfect one, and it is just from this imperfect resolution that, according to Freud, neurotic affections arise. The question whether a neurosis will result in a given case is essentially a quantitative one. The mind has the capacity of tolerating without harm a certain amount of stimulation from these internal impulses and desires that are not in unison with the ego, and when this limit is passed the energy derived from them flows over into neurotic manifestations. The mind has several methods for dealing with the energy of the anti-ego impulses successfully—that is to say, without the impairment of mental health—and it is only when these methods are inadequate to deal with the whole that neurosis ensues. Two of these methods may especially be noted. One is the deflection of the energy in question from its primitive and forbidden goal to another one in harmony with the more social standards of the ego; as every schoolmaster knows, sport is an excellent example of this. When the primitive goal was a sexual one, this process of deflection, here on to a non-sexual goal, has been given the name of “sublimation”, but there are similar refining and modifying processes at work in connection with all anti-ego impulses—e.g., cruelty. A second method is to keep the energy in a state of repression in the unconscious, the conscious mind refusing to deal directly with it and guarding itself against its influence by erecting a dam or barrier against it, known as a reaction-formation. Thus in the case of primitive cruelty, a cruel child may develop into a person to whom the very idea of inflicting cruelty is alien and abhorrent, the original impulse having been quite split off from the ego into the unconscious, and its place taken in consciousness by the reaction-formation barrier of horror and sensitiveness to pain and suffering. In such ways as these a state of practical equilibrium is attained in the normal, the power of the ego-ideal having proved sufficient either to utilise for its own purposes (by means of modifying) or to keep at bay, the impulses and desires that are out of harmony with it. In some people the state of equilibrium thus attained is of considerable stability, they have what is popularly called a reserve of mental and moral force with which they can meet disappointments, difficulties, and emergencies of various kinds in life, which means in practice that their capacity for readjustment to radically new situations is fairly elastic.