You'll understand what life is if you think about the act of dying. When I die, how will I be different from the way I am right now? In the first moments after death, my body will be scarcely different in physical terms than it was in the last seconds of life, but I will no longer move, no longer sense, nor speak, nor feel, nor care. It's these things that are life. At that moment, the psyche takes flight in the last breath.