We also know that reasoning must start with correct premise, this premise is called universally accepted truth and the theorem is deduced from it. But where does the universally accepted truth come from? Universally accepted truth cannot be gained by the means of reasoning, it has emerged in the practical activities that people do again and again. It is what everybody universally accepts as one kind of perception of objective reality. So the origin of genuine knowledge is in peoples daily practical activities and in the direct perception of the objective reality. So yiquan emphasizes that "one should not leave one's body", it means that one's body is the subject of research, its movement process is one kind of objective reality. That means you must by yourself go forward to directly feel this objective reality, and thereby gain genuine knowledge. This genuine knowledge is one kind of real existence in itself, it is also subjective cognition of objective, and thereby reality and concept are united. It also tells us: to push is exactly to push, to pull is exactly to pull, unite the concept and the action in your own body.
Much the same as what I've gathered from basic practice of the Alexander Technique and reading F. M.'s primary works.