From its opening passage, in which the sun sets and gives way to a “mournful gloom, brooding motionless over the biggest, and the greatest, town on earth [London],” Heart of Darkness conveys an ominous, pessimistic, and reflective mood. Conrad’s descriptive language emphasizes the Congo’s darkness and impenetrability, which represents the lawlessness and violence that reign there. From the moment Marlow approaches the Congo’s “colossal jungle, so dark-green as to be almost black,” he anticipates the dark truths about the human spirit that he knows to be hidden inside.
Surely enough, over the course of the novella, Marlow inches closer and closer to the “heart of darkness”—the terrifying truth that all humans are capable of atrocities, no matter how principled or civilized they consider themselves. His experiences are supposed to gradually erode the reader’s faith in human goodness and European colonialism, too. For instance, when he first arrives at the Central Station, he realizes that the General Manager is “a chattering idiot” and learns that Kurtz is ill. This makes him feel “weary and irritable,” because it suggests that his trip might be futile—he might have just trekked 15 days through the jungle for nothing. But he still hopes that Kurtz will live up to everyone else’s high praise. Of course, when Marlow finds that Kurtz is a homicidal madman, he realizes that all of his expectations were false. He calls the experience “withering to one’s belief in mankind.” In fact, the novella builds on its ominous mood by showing how the characters’ hopes are inevitably dashed, which suggests that people’s beliefs often mislead them.
While most of the novella conveys a constant but nebulous sense of dread, some passages are designed to shock the reader with glimpses of horrific violence. These moments bring humanity’s capacity for evil into sharp focus, like when Marlow’s African helmsman is brutally speared to death, or when Marlow realizes that Kurtz’s hut is surrounded by a fence of stakes with human heads on them. Curiously, Kurtz’s famous last words—“The horror! The horror!”—suggest that he went mad precisely because he could not stand to see (and partake in) the worst depths of human cruelty. Similarly, Marlow’s own close encounters with horrifying violence explain how he developed the gloomy, pessimistic mood that dominates the book. Of course, Conrad had very good reasons for horrifying his readers: he wanted to raise awareness about Belgium’s atrocities in the Congo and skepticism about the lofty claims of European colonialism.