In order to answer the long-standing question of why Hobbes does not justify a world government as a super-Leviathan, this paper examines Hobbes's accounts of international relations and the pre-civil state of nature. One common view tends to emphasize the differences between "the agents" in these two realms, namely states as artificial persons and individuals as natural persons; the other common view emphasizes the differences of "the relations between the agents". By re-examining Hobbes's account of the pre-civil state of nature, I argue that both of these common views are not sufficient. This essay intends to argue that if Hobbes's assumption of equality about the original state of nature is re-examined, it can be seen that what actually causes a state of war is not so much the equal ability of men as men's common tendency of considering themselves superior to others, namely vain-glory.