How can the absence of something be something? That, exactly, is the paradox of zero. If you go out and buy half a dozen eggs, then the number of eggs you have is six. If there are no eggs in the house, and you have already borrowed half a dozen eggs from your neighbour, then your egg count is minus six. But it seems a bit of a stretch, from there, to conclude that if you neither have eggs nor owe any eggs then, somehow, you do have a number of eggs, which is zero.