 According to contemporary science, there was a third nature, besides matter and energy, that was both immaterial, undetectable and capable of acting upon both matter and energy; as energy is capable of acting on matter and matter, of affecting energy.Such third kind was the basis for most religious theories and this theory was the bond that still allowed science and religion to have some common ground.In this chapter, Kardec explains "fluids" according to Spiritism and uses them to explain how spiritual phenomena worked.