If you are a human what are you? Are you brain in head? Or center of brain? Or a cell living in brain? Or an atom located at center of brain?
If we are made of atoms than we must know how atoms work. If we have 2 trillion cells in our brains we have to know how cells work. You may say we are electricity that flowing in brain but that means we are basicly electrons and samething that in the cable and you consuming for turning the lights on. You know how it is works but you dont know what it is. Than you are saying vampires doesnt exist. How can you be sure this universe is really exist and you are really a human?
This is a question