Joseph Conrad's novella Heart of Darkness refers to a common European name for Africa, the 'dark continent.' The continent was dark because of the skin of the people who lived there -- but also because it was assumed to be immoral, dark, and clouded in nature. To Europeans it was a cipher, and thus Conrad's decision to call his book Heart of Darkness also refers to the unknowing view of the colonists. Although Marlowe's view of the Africans he meets is troubling and often racist in nature, Conrad's title alerts the reader to the fact that Marlowe's view is inherently biased and subjective. The inability of people in the book to see one another clearly in a cross-cultural fashion is manifest in the African submission to Kurtz but also in Marlowe's disgust with Africa. Africa is impenetrable to the Europeans, and Europe is impenetrable and dark to Africans....

The heart of darkness is the heart of incomprehension, of utter cultural polarization: "We penetrated deeper and deeper into the heart of darkness. It was very quiet there. At night sometimes the roll of drums behind the curtain of trees would run up the river and remain sustained faintly, as if hovering in the air high over our heads, till the first break of day. Whether it meant war, peace, or prayer we could not tell."
Of course, Heart of Darkness also refers to the dark heart of man -- the dark desire for power. One possible reading of the book is that Africa 'makes' Kurtz dark, but it is equally possible to suggest that Kurtz is dark to begin with -- he comes to the Congo with the desire of making money, and finds the idea of living as an unopposed god in the midst of a foreign world even more attractive than returning to civilization.