Within the last fifty years the human mind has been awakening slowly to the fact that there is a world, invisible to ordinary powers of vision, existing in close juxtaposition to the world cognized by our material senses. This world, or condition of existence for more ethereal beings, has been variously called Spirit-world, Summer-land, Astral-world, Hades, Kama-loca, or Desire-world, etc. Slowly and with difficulty do ideas upon the nature and characteristics of this world dawn upon the modern mind. The imagination, swayed by pictures of sensuous life, revels in the fantastic imagery it attributes to this unknown and dimly conceived state of existence, more often picturing what is false than what is true. Generally speaking, the most crude conceptions are entertained; these embrace but two conditions of life, the embodied and disembodied, for which there are only the earth and heaven, or hell, with that intermediate state accepted by Roman Catholics, called purgatory. There is, therefore, for such minds, only two orders of beings, _i.e._, mankind, and angels or devils, categorically termed _spirits_; but what would be the mode of life of those spirits, is a subject upon which ordinary intellects can throw no light at all. Their ideas are walled in by an impenetrable darkness, and not a ray of light glimmers across the unfathomable gulf lying beyond the grave; that portal of death which, for them, opens upon unknown darkness, and closes upon the light, vivacity, and gaiety of the earth. The idea that the beings we would term _disembodied_ do actually inhabit bodies of an aerial substance, invisible to our grosser senses, in a world exactly suited to their needs, surpasses the comprehension of an ordinary understanding, which can conceive only of gross matter, visible and tangible. Yet science begins to talk of _mind-stuff_, or _soul-substance_, in reality that ethereal substance which ranks next to dense matter, and which it wears as an external, more hardened shell. For there is space within space. Once realizing the existence of an _inner world_, we shall find that all our ideas concerning space, time, and every particular of our existence, and the world we live in must become entirely revolutionized.