Nothing can be taught because knowledge does not exist outside but within us. What this means is that the Wisdom that has gone into the worlds is there within us as much as it is there within each atom of existence.
But when we sincerely try to understand something, when we put in some effort to learn and know, then as a result of this effort this now closed door of Knowledge opens and we begin to slowly understand little by little because we see things in this light that is dawning upon us.
This Light initially comes in us filtered through reason and hence we must exercise reason to understand but as we grow in consciousness higher and better modes of seeing and understanding develop and we can see and understand better and better.
A good teacher or even a good book lends us that light for a moment. But a truly great spiritual Master and the greatest of books open the doors of inner Knowledge within us so that we can access it just as the teacher or the author of the book could do.
About Savitri | B1C1-09 Advent of the Divine Mother (p.4)