II. Haeckel's “Riddle of the Universe” and Theosophy

The ordinary man, held in bondage by his senses, cannot possibly gain admittance to this realm. It is only by the aid of certain methods of investigation that the spiritual world opens to the seeker. Thus, man must transform himself into an instrument for those higher powers, one able to penetrate into worlds hidden from those still enthralled by their physical senses. To such as can accomplish this, visions of a quite distinctive nature will appear. The ordinary human being is not capable of seeing for himself, or of consciously recognising things about him, when his senses are wrapped in slumber; but when he applies occult methods of investigation this incapacity ceases, and he begins to receive quite consciously impressions of the astral world.