"God is dead" is something very different from "God does not exist," and Zarathustra alludes at several points in the book to the fact that God was once alive. This God that was alive provided a meaning and a morality for the lives of the people who believed in him. By saying "God is dead," Nietzsche is suggesting that God no longer serves as this ultimate basis in Western culture. We can no longer justify our claims and our assumptions by an appeal to God; now God himself is something that we must justify if we wish to believe in him. Thus, Nietzsche's claim cannot be refuted by an argument that God does in fact exist. Rather, if we wanted to disagree with Nietzsche on this point, we would have to argue that Western culture still bases most of its claims on religion, an argument which we would probably have trouble carrying off successfully.