What you believe matters, however. It’s all anyone has to act on. And since what you do is who you are, your actions define you. If you don’t believe anything is true simply because you can’t logically prove what’s true, you won’t do anything. You won’t be anything. You’ll end up spending your life in a rocking chair looking out at the horizon waiting for an answer that never comes. You might as well be dead. It’s an old philosophical problem.