88. Since, then, without a perception of what correspondence is there can be no clear knowledge of the spiritual world or of its inflow into the natural world, neither of what the spiritual is in its relation to the natural, nor any clear knowledge of the spirit of man, which is called the soul, and its operation into the body, neither of man's state after death, it is necessary to explain what correspondence is and the nature of it. This will prepare the way for what is to follow.