4. The fluidic elements of the spiritual world elude our instruments of analysis, and the perception of our senses. They are things suited to tangible and not to ethereal matter. Spiritual substances belong to a midst so different from ours that we can judge of them only by comparisons as imperfect as those by which a man born blind seeks to form an idea of the theory of color.
But among these fluids a few are intimately joined to corporeal life, and belong in a measure to the terrestrial universe. In default of direct perception of cause, it is possible to observe the effects of them as one can observe the fluids of a magnet, which no one has ever seen, and acquire some knowledge of their nature with precision. This study is essential; for it is the key to a multitude of phenomena, which are inexplicable by the laws of matter alone.