It will hardly be necessary to say that the above is not intended to discourage the study of phenomena; for those who have not the power of reaching higher will gain nothing by remaining ignorant of external appearances; but it is intended to show that a science referring merely to the phenomena of terrestrial life and ultimate results is not the summit of all possible knowledge; for beyond the realm of visible phenomena there is a far more extensive realm open to all who are capable of entering: the realm of truth, of which only the inverted images are seen in the kingdom of external phenomena.
The natural science of the ancient mystics, owing to their deeper penetration into the so-called supersensual realm, was not limited to the world which we see with our bodily eyes; for they recognised four worlds or planes of existence within each other, each of them having its own forms of life and inhabitants, namely:—
(a.) The physical visible world, being only the reflection of the three higher ones.
(b.) The astral world, or the psychic realm.
(c.) The world of mind, or the spiritual realm.
(d.) The divine state, the kingdom of God, or the celestial world.
As we perceive the existence of a mineral, vegetable and animal kingdom upon the sensual plane,[12] so they, by the faculty of the developed inner sight perceived and described within this world four kingdoms, or four spiritual, and to us invisible, states of existence, which in their outward manifestation are called: Earth, Water, Fire, Air.
“We will show you that we are not the only intelligent beings possessing the world, but that our possessions extend over only one-fourth of it. Not that this world were three times greater than we know it to be; but there are in it still three-fourth parts which we do not occupy, and their inhabitants are not inferior to us in intelligence; the only thing of which we may be proud, is that Christ (the light of divine wisdom) has taken his habitation in us and clothed himself in our form, as he might have chosen another nation (another class of Elementals) for that purpose.” (Paracelsus, “Of the generation of conscious beings in the universal mind,” I. Preface)
All this, however, does not strictly belong to the present purpose of this work, and is merely mentioned so as to make room for the conception that nature is far greater than the limits assigned to it by material science, and that, as a certain philosopher said: “that which is known is only like a grain of sand on the shore of the ocean of the unknown.”