" Envy, lust, sensuality, lies, and all known vices are the negative, “dark” aspect of the unconscious, which can manifest itself in two ways. In the positive sense, it appears as a “spirit of nature,” creatively animating man, things, and the world. It is the “chthonic spirit” that has been mentioned so often in this chapter. In the negative sense, the unconscious (that same spirit) manifests itself as a spirit of evil, as a drive to destroy. As has already been pointed out, the alchemists personified this spirit as “the spirit Mercurius” and called it, with good reason, Mercurius duplex (the two-faced, dual Mercurius). In the religious language of Christianity, it is called the devil. But, however improbable it may seem, the devil too has a dual aspect. In the positive sense, he appears as Lucifer—literally, the light-bringer. "

― C.G. Jung , Man and His Symbols