本文檢視在後冷戰時代石油美元機制對美國霸權之影響，並關注美國領導地位在1991年波灣、2003年伊拉克與2011年利比亞等戰爭中的角色。在處理國際事務中，美國霸權逐漸採行單邊行動，因而產生合法性危機之質疑。因此自1990年以來，美國便宣稱願意承擔昂貴之經濟成本與犧牲其國家之利益，以便與他國建立聯盟共同對抗流氓國家之威脅。美國能以維繫穩定之國際經濟秩序，與贏得反恐作戰之合法性名義發動先制戰爭。為了理解這一看似非理性之行為，根基於Pierre Bourdieu關於象徵性資本之概念上，我們提出「炫耀性利他主義」以解釋美國與其盟國採取昂貴成本行動背後的原由。此外，我們更進一步指出傳遞此種「炫耀性利他主義」信息之目的，在於維繫「石油美元」此一能捍衛美元信用的系統。如此，透過作為全球儲備貨幣之美元，美國將能提升其霸權地位。

This paper explores the impact of petrodollar mechanism on the hegemony of the United States in the post-Cold War era. It particularly focuses on the two wars against Iraq respectively in 1991 and in 2003 and the Libyan war in 2011, all under the leadership of the U.S. The U.S. hegemony has been experiencing a legitimacy crisis caused by its increasing tendency towards unilateral actions in international affairs. In order to form alliances among Western nations to confront the rogue states, the U.S. government has demonstrated its willingness to bear economic losses and sacrifice its national interests ever since the 1990s. The United States was engaged in preemptive wars on terrorism to regain its legitimacy of maintaining a stable international economic order. The victories proved to be costly. To analyze such seemingly irrational behaviors, we propose the concept of "conspicuous altruism," based on Pierre Bourdieu's notion of symbolic capital, to find the rationale underlying the costly military actions taken by the U.S. and its allies. We further argue that the "conspicuous altruism" signals the U.S. intention to maintain the petrodollar system, which then secures the credibility of the dollars. The U.S. can reaffirm the Dollar's status as a global reserve currency, thereby enhancing its hegemonic status.