拳有勢者,所以為變化也。横斜側面,起立走伏,皆有墙戶,可以攻,故謂之勢。拳有定勢,而用時無定勢。然當其用也,變無定勢,而實不失勢,故謂之把勢*
Fists have a posture, which implies changes. Transversal, oblique, sideways or frontal, getting up, standing, moving or lying prostrate, everything has walls and doors, attack being then possible, therefore we talk about posture. Fists have fixed postures, but when boxing there is no fixed posture. So that it undertakes its own usefulness, changes knowing no determined posture and yet one actually not losing posture, which is the way to be skilful in the art.
戚繼光曰:“操手足之號令易,而操心之號令難;有形之操易,而不操之操難”**
Qiji Guang said: " The command to practice the hands and feet is easy, but the one to train the heart hard; practicing form is easy, but the drill with no drill hard"
For old internal practices, fighting was chaos, hence no rule, while training, to compensate, had to be made with method, hence rules and order. Training with rules for the chaos was another oxymoron to be solved. Indeed, because fighting was chaos, one would aim to reach the formless even though training was ruled by form. There are therefore a lot of sayings in Chinese martial arts that, as oxymorons, ask the students to do the opposite in fighting of what was done while training.