Manifest destiny was the expansionist belief in the 19th-century United States that American settlers were destined to expand westward across North America, and that this belief was both obvious ("manifest") and certain ("destiny"). The belief is rooted in American exceptionalism, romantic nationalism, Anglo-Saxonism, and nascent ideas of white chauvinism, implying the inevitable spread of republicanism and the American way. It is one of the earliest expressions of American imperialism. According to historian William Earl Weeks, there were three basic tenets behind the concept: The assumption of the unique moral virtue of the United States, the assertion of its mission to redeem the world by the spread of republican government and more generally the "American way of life", and the faith in the nation's divinely ordained destiny to succeed in this mission.