5. During the incarnation the spirit acts upon matter through the intermediation of its fluidic body, or perispirit; it is the same when discarnated. It accomplishes as spirit, and by the measure of its capacities, that which it did when on Earth; only, as it has no longer for an instrument its mortal body, it serves itself, when necessary, with the material organs of an incarnate being who is what we call a medium. It does as he does, who, unable to write himself, employs a secretary, or who, not understanding a language, is served by an interpreter. A secretary and an interpreter are mediums for an incarnated being, as a medium is the secretary or the interpreter of a spirit.