That person lacks mastery who is held by that which he sees. He cannot help seeing it, although he does not want to see it. But the one who has his sight in his hand sees what he wants to see, and what he does not want to see he does not see. That is mastery. As it is true of the eyes that what is before them they see and what is behind them they do not see, so it is true of the mind: what is before it it sees and what is behind it it does not see. And so a person who sees may see one side, while always the other side is hidden. Naturally therefore, if this objective world is before his eyes, the other world is hidden from his sight, because he sees what is before him; he does not see what is behind him. And as it is true that what is behind him a person can only see by turning his head back, so it is also true that what the mind does not see can be seen by the mind when it is turned the other side. What is learned in esotericism, in mysticism, is the turning of the mind from the outer vision to the inner vision.