It could work like this. If natural selection can arrange that you enjoy the feeling of existing, then existence can and does become a goal: something—indeed, as we’ll see, some thing—you want. And the difference between your wanting to exist and simply having some kind of life instinct is that, when you want something, you will tend to engage in rational actions—flexible, intelligent behavior—to achieve it. You will do things that are not rewarding in themselves but that are calculated (on some level) to deliver the goal. You may even do things that are punishing—including going through pain.
— Humphrey, Nicholas. Soul Dust: The Magic of Consciousness. Princeton, New Jersey: Princeton University Press, 2011.
