“The action of the man on the horse, and the reaction of the horse to man, are subject to certain principles, to some cause which is located in each, but it must not be developed by chance, if one wishes to control with greater accuracy. The first law of this correctness is the intimate union of two individuals. This union requires on the part of the rider a proper position and action and, on the part of the animal, a boundless subordination with a prompt and blind obedience, at least as long as laws of its structure are not violated.”
Dupaty de Clam (Craig Stevens translation. From the art and Science of Equitation 1776
Here it is in a nutshell. The union of body and mind subjugated to the mechanical and psychological realities of the horse. We must look to the cultivation of the skill of listening to the horse’s movements to find the secret of the correct aids, for only then can the horse’s mind be at ease.
This is the dressage which any method cannot find. Dressage is not the invention of the human mind but the human mind which has found the harmony and the discipline which nature imposes.
Good instruction in dressage consists in the introduction of the student to the nature of one’s own mind. Correctness and clarity in dressage can only be found when a harmonious and peaceful mind extends itself with intelligent compassion to the horse.