Black's attack on the Principle of Identity of Indiscernibles has occupied the center stage of the debates between bundle theorists and substratum theorists. Metaphysicians has thought that this attack is crucial, and that substratum theory is superior to bundle theory. This paper aims to show that black's argument is not decisive. For that, this paper will demonstrate two facts : first, if we introduce one observer into black's universe, his argument would go into fail ; second, black's argument has the fallacy of begging question. By this strategy, this paper will show that bundle theory is still sound metaphysical theory.