Thank you for the reply. So I guess the reason I ask this is because I've seen firsthand that that applying taji philosophy to martial arts is incredibly powerful in terms of practical self-defense as well as spiritual cultivation. I don't wanna sound too silly, but my teacher is basically unbeatable, unless the opponent is another high level internal artist. His reflexes are so quick, and his throws and blows are so powerful, I couldn't picture even a strong MMA guy besting him in a no-rules fight. He is incredibly sensitive, and can do very subtle things that feel very powerful, feeling and controlling my center as soon as he makes contact. While staying utterly relaxed, he can neutralize an attack and deliver several deadly counterattacks at very rapid speed. As long as he maintains that calm, empty mind-state, he is basically in invincible demon warrior. And he puts himself at the lower-mid level of what's possible. It seems there are a few particular skills (moving from the dantian, relaxed jin-strength, listening energy, yielding/following to name the basics) that when cultivated past a certain threshold, and combined with certain "secret" theories derived from taiji philosophy, can be applied to martial arts to such great effect as to make the practitioner damn near invincible against an untrained attacker, or even multiple attackers. In terms of life and death self-defense, for someone who may be a professional soldier for example, it is in fact extremely practical. It seems to me that these skills are directly tied with Daoist philosophy. I can't see how these skills could be cultivated to a high level without applying Daoist principles. Is it your opinion that these skills didn't fully develop until the 18th or 19th century? It seems more likely that they were closely guarded and just not often written about. I would think characters who were known as such skilled fighters like Guan Yu may have trained similar skills. Hopefully you've experienced or witnessed the type of skills I'm talking about; it's not something you see in every taji school. Apparently even the official Yang family lineage has lost the full, true art, since Yang Chengfu died before he could teach his kids. My teacher says the Chen family has lost it as well but I suspect maybe they just don't show it off or teach it to outsiders.