I was tickled by verse 46 when it said that it is "degrees" by which the journey is studied, applied and gained through the very SAME PROCESSES used in the mystery schools. The Rosicrucian Order A.M.O.R.C. which I initially applied myself to has three primary "degrees": Atrium 1. 2. 3. Then there are the Nine Temple degrees, which I know nothing about.
All in all your OP "Empirical Science",is the first order of observation in the Sutras; then the "Philosophy of Science", the combination of study by intellect, sensory awarenesses, and finally, the "spiritual experiences" of, through and in the application of the Soul toward "higher" knowledge, all fits together perfectly. The latter books explain the processes more fully and truly, as applied.