In philosophical terms, asking about the purpose of life may indeed be analogous to asking why unicorns are hollow. But in psychological terms, that’s an anaemic comparison. People aren’t normally very preoccupied with uncovering the secret attributes of unicorns; we accept that unicorns don’t exist and, as a consequence, whether they’re hollow or solid doesn’t exactly weigh on our thoughts. The same doesn’t necessarily hold true for God, however. Many people don’t believe in God, yet they still ask themselves about the purpose of life and can’t easily shake their curiosity about this seemingly grand and obscure mystery. Even though we know our biological facts and have managed to emotionally disencumber ourselves from the strappings of the Cross, or flung off our yarmulkes, turned our hijabs into throws, and all the rest, the question of why we’re here still occasionally rises up in our thoughts like a case of hives—and it’s an itchy rash that science just can’t seem to scratch. So the real mystery lies not in why we are here on this earth, each as distinct individuals; instead, the real mystery is why this purpose-of-life question is so seductive and recalcitrant in the face of logical science.
– Jesse Bering, The Belief Instinct: The Psychology of Souls, Destiny, and the Meaning of Life