The organism of every living being is an instrument intended exclusively to provide its source with a particular, specific opportunity for life. What this opportunity for life amounts to is thus based on the capacity of this organism. Outside the bounds of this capacity no being can normally experience physical existence. For this reason a fly cannot live at the bottom of the ocean, and a deep-sea fish cannot live in a burning desert. They must each remain where they are, since their organism cannot give them an opportunity for life under other conditions than those they are built to meet.
      If the being were to leave the vital conditions that its physical organism is built for, its physical existence would end, and we say that it died. But this death holds true only of its physical existence. Its I and the invisible part of its existence connected to this I, which means its consciousness or world of thought still exists. But since the physical organism is dead the being can no longer convey through it the existence of its I and its consciousness. And now there is therefore a physically empty space where previously it filled physical space with its manifestation. But it still lives in this empty space, manifesting itself and experiencing life through its appropriate spiritual organism along with all the other beings of the same status until it can again be born on the physical plane. Since this existence, as shown here, is inaccessible to physical senses, it is a matter of course that it can manifest itself physically only as invisible.
      And it is this invisible world we experience as the empty space of the universe. In this empty space is thus hidden the real primary world. From here the beings are born into the physical world and to here they return when they leave this world at death. The physical world is merely a secondary world. The physically invisible, spiritual world or empty space of the universe is thus the primary area of life. It is the domain of eternal life.