In Joseph Conrad's story "Heart of Darkness," Charlie Marlow reveals his reason for wanting to pilot a steamboat up the Congo river explicitly. But through the telling of his story, the reader becomes aware that there are implicit reasons for his journey, as well, or at least instances in which the journey changes him in ways he did not expect.
Charlie Marlow explains:
"‘Now when I was a little chap I had a passion for maps. I would look for hours at South America, or Africa, or Australia, and lose myself in all the glories of exploration. At that time there were many blank spaces on the earth, and when I saw one that looked particularly inviting on a map (but they all look that) I would put my finger on it and say, ‘When I grow up I will go there.’ The North Pole was one of these places, I remember. Well, I haven’t been there yet, and shall not try now. The glamour’s off. Other places were scattered about the hemispheres. I have been in some of them, and … well, we won’t talk about that. But there was one yet—the biggest, the most blank, so to speak—that I had a ‘True, by this time it was not a blank space any more. It had got filled since my boyhood with rivers and lakes and names. It had ceased to be a blank space of delightful mystery—a white patch for a boy to dream gloriously over. It had become a place of darkness. But there was in it one river especially, a mighty big river, that you could see on the map, resembling an immense snake uncoiled, with its head in the sea, its body at rest curving afar over a vast country, and its tail lost in the depths of the land. And as I looked at the map of it in a shop-window, it fascinated me as a snake would a bird—a silly little bird. Then I remembered there was a big concern, a Company for trade on that river. Dash it all! I thought to myself, they can’t trade without using some kind of craft on that lot of fresh water—steamboats! Why shouldn’t I try to get charge of one? I went on along Fleet Street, but could not shake off the idea. The snake had charmed me."
In the above quote, readers see that within Charlie Marlow is a wanderlust that has been central to his being since boyhood. He describes the Congo as twisting and coiling like a snake--one that charmed him. This analogy to being hypnotized by the region, as well as his reference to the area having changed from a white space of imagination to a place of darkness--literally, ink on a map, but metaphorically, savagery in all its forms--suggests that the darkness of Charlie's own soul is drawn to the heart of this darkness which is Africa.
Charlie Marlow goes on to describe the death of his predecessor, Fresleven, who was seen as a gentle and good man on the continent of Europe. His goodness is questionable when readers consider his treatment of native people, and his death is violent at the hand of those he has made subordinate to him. All of the native people abandon the village after his death due to their superstitions.
Charlie's aunt, who has helped fund his expedition, expects Charlie to bring light into the darkness she believes exists in Africa. He recounts:
"She talked about ‘weaning those ignorant millions from their horrid ways,’ till, upon my word, she made me quite uncomfortable. I ventured to hint that the Company was run for profit."
Charlie makes it clear to readers he has no nobleness of purpose for going to the Congo. He is going to satisfy his need for adventure, and perhaps his curiosity about the savage land. He notes his strange feelings of uneasiness--something he had never experienced before embarking on an adventure.
"In the street—I don’t know why—a queer feeling came to me that I was an imposter. Odd thing that I, who used to clear out for any part of the world at twenty-four hours’ notice, with less thought than most men give to the crossing of a street, had a moment—I won’t say of hesitation, but of startled pause, before this commonplace affair. The best way I can explain it to you is by saying that, for a second or two, I felt as though, instead of going to the centre of a continent, I were about to set off for the centre of the earth."
His reference to the center of the earth and his references to the map being now in darkness hint that he is journeying to the heart of humanity in a metaphorical way. He learns that the heart of humanity is a heart of darkness. Colonists from all over Europe have destroyed the land in their desire to take what they could profit from, including enslaving humans. People are treated as savages, punished in unimaginable ways. His reference to Belgium as a "whited sepulchre" is reminiscent of the Biblical book of Matthew where Jesus called the Pharisees--a group of religious leaders who believed they were better than others--whitewashed tombs, full of dead men's bones. Freslaven's bones were literal in the story, but there were many examples of whitewashed tombs--people who looked good on the outside but had hearts of darkness.