The Civilizing Mission
The earliest and, to some, most important reason for establishment of European colonial empires had been to spread Christianity. By the later 19th century, this idea had evolved into a broader goal: spreading what most Europeans believed to be their higher form of civilization. Most Europeans of this time believed that their continent had become more economically, politically and culturally advanced than Africa and Asia, because the people there Europeans believed were "primitive" and uncivilized. They believed therefore that Europeans had a "civilizing mission" to spread their way of life around the world.
This idea was linked by many to the theories of Charles Darwin on the evolution of species. Some, like Karl Pearson, modified Darwin's theory into a theory of "survival of the fittest." This modified theory, known as social Darwinism, held that some people were naturally selected to rule over others. Social Darwinists applied this to mean that the more "civilized" race of Europeans should rule over all the "less civilized" people of the world. To support this argument, social Darwinists pointed to the racial difference between Europeans and Africans.
They considered the black skins of people from central and southern Africa to be evidence that Europeans were genetically more advanced. They therefore considered it the historical responsibility of Europeans to spread their superior culture to the rest of the world. This idea was expressed as the "white man's burden."