Ancient wisdom is wisdom that has existed from the beginning, and continues to exist unchanged by time and circumstances. It is wisdom that is true, as air is true. According to ancient wisdom, when two worlds become one, they no longer can be separated. They have to remain as one. To separate them would be to seek to destroy them. Similarly, when two people become one, they no longer are two and cannot be separated. Their spirits remain united as one.
When a spirit inhabits two bodies, the two persons with the same spirit are identical twins. They are united in spirit, though existing as two individuals. When a person makes a decision to surrender to God and accept Jesus' cleansing, they are saying that they want to be cleansed sufficiently so as to become one with God. They want to have the nature and likeness of God. In response, God fills and imbues (saturates) them with his Holy Spirit. Because of that oneness, they know that God will render them immune to spiritual death, as long as they maintain the unity of the spirit.
Immunity from death is what every spirit desires. The spirits know that in spiritual death, they remain awake and fully conscious, according to consciousness as we know it. They remain in a perpetual state of conscious infancy, never growing or maturing spiritually, and never becoming capable of changing their dire circumstances. They are dead to God in that they can never again know him, and they are dead to the world.