Is the U.S. an empire? This paper will apply the ‘concept/conception’ analytical distinction to the notion of empire, in order to compare evolving conceptions of the concept throughout some of its instantiations in Western history (from the Athenian Empire to the Macedonian, Roman, Spanish, British, and American Empires). My working definition of empire will comprise the ideas of ‘civilization’, as developed by M. Ignatieff, and of the ‘Nomos of the Earth’, coined by C. Schmitt. The foremost features of the American Empire are its informality and its reluctance to embrace its nature. Informality was first developed by the modern European empires in order to harness private initiative and the free movement of capital. Informality in the American Empire is mirrored by its selective attitude towards international law and institutions. Reluctance results from Americans seeing their values as ‘natural’, ‘self-evident’, and universal. Yet, it is still preferable to international anarchy.