Foundation Establishment is a complex project involving many rigorous theories, enough to write a thousand papers and open a separate course.
Fang Zhou is still a novice among novices on the cultivation path, relying on some tricks to get where he is today, unlike other cultivators who progressed step by step with solid practical and theoretical foundations.
Fang Zhou is fairly adept at practical operations, but he's clueless when it comes to theory, so he doesn't fully understand the various forces involved in the Foundation Establishment Realm.
However, based on his own understanding, the Qi Refining Realm is about using spiritual energy to nourish and strengthen the body, while the Foundation Establishment Realm is about transforming the body with spiritual energy. In short, it's like a complete transformation, transcending the ordinary.
