In order for there to be any potential, there must be something actual. Pure potentiality is pure nothing, and you cannot get something from nothing. So according to your reasoning, if there is only a potential human being, then there would never be an actual human being. How did any of us ever come to be? You've just proven that none of us actually exist. But we DO actually exist, proving that your argument is fallacious. There must be something actual for there to be potential. What is the actual thing that has potential?