Should an instinct be denied its expression and all ideas connected with it be repressed into the subconscious, trouble will ensue. The lower reaches of a river can be emptied by the simple expedient of placing a dam across its channel, but this does not solve the problem of the surplus water, which gathers head behind the obstruction till it bursts its banks and makes a morass of the upper reaches. If it is necessary to deflect a river from its bed, then an alternative course must be provided, for the water continues to come down from the hills and must by some means be disposed of. It is precisely this engineering problem that the psychotherapist has to deal with. We know that a large percentage of mental and nervous disorders are caused by the repression of the sex instinct. This great instinct, in its mental and physical aspects, is so fundamental and so powerful that it cannot with safety to the individual be entirely repressed, nor with safety to society be given free rein, and we are on the horns of a dilemma, for social laws demand that it shall only be expressed under very limited conditions--those of legal marriage, and even then not to an unlimited extent; and nature demands that it shall be expressed as soon as the physical organs of its manifestation are sufficiently developed to function. The average man solves this problem for himself by conniving at the maintenance of a pariah class of women whose very existence is socially ignored and is a fertile source of misery, disease, and crime; but for women, unless they are prepared permanently to join the pariah class, a social safety valve does not exist, and we find among them a much higher percentage than among men suffering from those nervous troubles that are due to a repression of the sex instinct, and this also applies to men who, whether from idealism or fear of disease, do not avail themselves of a compromise. This problem would prove as intractable in the future as it has in the past were it not that we now know that the law of transmutation of energy from one form to another is as true for psychology as it is for physics, and sex force can be utilised for other purposes than physical reproduction. This process of conversion is technically known as SUBLIMATION. This is one of the most important discoveries of modern psychology, for it provides the solution to grave social problems that menace the fabric of civilisation. How, in actual practice, can this result be achieved?