Self-knowledge can be divided into four kinds, of which the first is knowledge of this physical vehicle which we call our body: how this vehicle has again two aspects, the head and the body, the former for knowledge (for all the special organs of perception are situated in the head), the latter for action. Knowledge of the physical body does not end with the knowledge of anatomy; in this body there are also centers which are the organs of intuition. In so far as science recognizes them they are nervous centers, but what a mystic sees in them is the subtle power of perception. And therefore to a mystic the human body is a more perfect instrument than a wireless receiver, for that is a dead thing compared with the human body; the body is a living wireless receiver if it is prepared for that purpose.