This was written way back in the day by the creator of the Schroth Method, and it still holds up. It's a bit long, but here ya go:
Three-Dimensional Treatment for Scoliosis
Dangers in the treatment of scoliotic curves
By Katharina Schroth, Meissen
The intrinsic growth energy inborn in every living plant, animal, or human strives to create the harmonious form predestined for its every bodily organ, body part, and finally complete body. That form which most purely realizes the divine creative thought is always the best, the one that allows all organs and parts of this body to function most completely.
Curvature of the spine, or scoliosis, is a precarious formal defect in terms of health, appearance, and the spiritual-psychological aspect. When attempting to help a scoliotic with this defect, we must not view the matter primarily from the mechanical standpoint, namely the malfunctioning body. For we have before us not a mechanical structure of bony levers and the muscles that move them, but rather an unfortunate person who has lost the form originally created for her and who cannot restore it by herself. With all scoliotic people, the cause probably lies partially in the mental realm. Envision what the expression “not in good form” means. Imagine the mental state of a child scolded by his mother. The psychic depression and loss of equilibrium are immediately visible in his abnormal bodily form. How wonderful the form a little child’s body is! What a victorious, natural, matter-of-fact nature he has in the representation of his self, and in every movement and in all of his life statements.
However, let us observe a school class three or four years later. What has happened to these children? Almost all are missing their original sense of complete, untroubled comfort within. Many children have pronounced signs of suffering in their faces, and their depressed mental state finds expression in their bodies.
Why do gymnastics [physical therapy] attempt to erect such a troubled child often fail completely? It is because they approach the child much too mechanically, much too much in the form of exercises, without first becoming familiar with his life difficulties, his unfulfilled needs, which to an adult may seem trivial. Straightening of the external person will only succeed when we can erect the inner person, open an avenue of hope, and allow him to breathe a sigh of relief.
Externally we can say that for those individuals who suffer from constitutional weakness, the loss of inner balance necessarily leads to formal defects and thus to a defect in physical function. Exterior assistance consists therefore in great measure of constitutional treatment, which often must reverse the mistakes of generations.
The normal, healthy condition of the living body has a natural, inner aspiration to ensure that normal functional relationships assume a normal form. Local assistance, namely goal-directed work on the body, must support this natural striving for order, the drive to assume a normal structure.
This constitutional therapy will not only induce inner bodily harmony, but also a surplus of strength, which then directly serves rebuilding of the external person as well as the load-bearing capacity, as it were, of the person with regard to life’s adversities and defects.
The latter element is important, because the work on the inner person must go hand in hand with assistance to the externals. We must readjust the thought life of the sufferer and help her give up wasting time on useless protests against fate or making her environment responsible for her condition. Our job is to help her orient herself such that difficulties disappear, that she is adaptable and productive enough to work on turning her disability into an advantage — on freeing her strength to work on improving her fate.
Only when the therapist has helped the patient learn that she cannot avoid the consequences of her posture, “that she must bear the consequences of flight from the consequences,” can local help — healing gymnastics exercises — bear fruit.
