The essence of study is to learn from the prototype of the subject. For example, if you learn coding, you learn from the v0.01 version of the code base. If you learn empirical study, you have to know the in-depth theory why it is done in this way. If you learn set theory, you learn the traditional one and what changes has Von Neumann made to sew up the gap of foundations of mathematics. Everything gets more complicated and obscure as it evolves and if you don’t know what it is like in its origin, you will never know how it evolved, what adjustment has it made and why it became what it looks like for now. The reason why it be itself lies on the trace of updates. Nearly everything, every knowledge has the instructions out there. The difference is that it is explicit for books while implicit for other crafts. You have to find the hidden trace of the introductions from various materials.