Theosophy, or Divine Wisdom, is a hidden science. It is also the Science of the Hidden. Its field is the invisible. It maintains that everything perceived by the senses has a secret depth; the surface of objects, their "exterior horizon", is but the boundary of a "darkness filled full with visibility", a phrase used by Maurice Merleau-Ponty. This "second visibility" makes it possible for those who have developed the necessary psychic faulties to explore the occult dimension of the universe. It is this interior horizon of things that is the object of theosophical investigation.