Union w/ Physical Body | Functions
If you have read the subsection on What Are Spirits (see link on menu bar at left), you will recall that the human being is formed of three essential elements. As Kardec writes¹, "The first element is the body, which humans have in common with animals. As such, the body is animated by the same vital principle that exists in animals. The second element is the soul or incarnate spirit, of which the body is the habitation and through which it acts. The third element is a semi-material form called the perispirit; it constitutes the spirit's innermost envelope and unites the spirit with the body."
The perispirit is the spiritual body ̶ the spirit's fluidic, vaporous, quintessential, semi-material envelope, having both flexibility and expandability. Under the command and direction of such spiritual body, which accompanies the spirit throughout its entire existence², the spirit exercises important functions. It is this spiritual body that allows the spirit to act upon matter, and for matter to act upon it.