" The soul of one person can become intertwined with the soul of another. Aristotle is supposed to have said: “What is friendship? It is a single soul dwelling in two bodies.” The ancient term for such a relationship is “soul friend,” defined as one with whom I have no secrets. The ancient Celtic Christians said that “a person without a soul friend is like a body without a head. "

― John Ortberg , Soul Keeping: Caring For the Most Important Part of You