Nature has a constant, ominous presence throughout Heart of Darkness. At many points in his story, Marlow discusses the natural world and the impact it has on him and the other Europeans he encountered on his journey. Importantly, Marlow’s interest in nature is not simply descriptive. His discussions of nature never emphasize what the Congo River and the forest that surrounds it look like. Instead, the fascination Marlow has with nature relates to his own internal experience. That is, instead of treating the natural world as something that is external to him, Marlow tends to represent nature as a manifestation of his own feelings. In the context of literature, such a tendency to attribute human feelings and actions to nature has a name: the pathetic fallacy. The pathetic fallacy, which could also be called “emotional falseness,” is most often associated with the British Romantic poets of the nineteenth century. These poets often personified inanimate objects to describe how those objects made them feel. Conrad draws on this technique in Heart of Darkness, but instead of using the pathetic fallacy to evoke feelings of beauty or melancholy, he uses it to conjure a sense of nature as ominous and threatening.

In Marlow’s story, the Congo River serves as an important symbol: it is the conduit that ushers him and his crew ever further into the “heart of darkness.” Curiously, Marlow imagines the river not just as a passage through space, but also as a passage through time: “Going up that river was like traveling back to the earliest beginnings of the world, when vegetation rioted on the earth and the big trees were king.” In this description, the Congo River becomes more than a simple waterway; it becomes a time machine that can return passengers to a strange primeval time when plants, not animals, ruled the world. As Marlow indicates, following this passage into the remote past proves disorienting. He tells his audience: “The broadening waters flowed through a mob of wooded islands; you lost your way on that river as you would in a desert . . . till you thought yourself bewitched and cut off for ever from everything you had known once.” The disorientation Marlow speaks of here is spiritual as well as physical. In going back in time along the river, one risks losing oneself.

If Marlow sees the natural world as disorienting, it is because he sees nature as a kind of “surface,” one that conceals a hidden mystery that he can never quite figure out. This disconnection between how things appear and what they really are can be confusing, even terrifying. When reflecting on the silence of the river and the forest, for instance, Marlow observes: “this stillness of life did not in the least resemble a peace. It was the stillness of an implacable force brooding over an inscrutable intention.” Here, Marlow indicates that the apparent stillness of the world around him actually conceals some unknowable but powerful force that is incapable of being appeased. Nature is therefore threatening: “The great wall of vegetation . . . was like a rioting invasion of soundless life, a rolling wave of plants, piled up, crested, ready to topple over the creek, to sweep every little man of us out of his little existence.” Recalling his idea that plants ruled the primeval world, here Marlow imagines that the “wall of vegetation” can release a devastating wave of energy, one that is capable of wiping out all humans.

As he and his crew press further into the wilderness, Marlow begins to associate nature with the African people and their apparent savagery. He first makes this association as his boat comes under attack. Marlow looks into the forest, where he sees a wash of moving body parts and vegetation: “I made out deep in the tangled gloom, naked breasts, arms, legs, glaring eyes—the bush was swarming with human limbs in movement.” The Africans are visually “tangled” up in the forest, and hence symbolically inextricable from it. Later, at the Inner Station, Marlow witnesses a number of tribespeople exiting the forest: “as if by enchantment streams of human beings—of naked human beings—with spears in their hands, with bows, with shields, with wild glances and savage movements, were poured into the clearing by the dark-faced and pensive forest.” The use of the passive voice (i.e., “were poured”) is important, as it makes the forest the acting subject of the sentence, not the Africans. Grammatically, then, the forest has all of the power. Although Marlow is not explicit on this point, this example suggests that the forest is the source of the Africans’ apparent savagery.

If the natural world is what makes Africans “savage,” then it is also what threatens to sap Europeans of their civilized essence. Marlow suggests this most clearly when recounting the night Kurtz escaped into the forest. Kurtz flees deeper into the wilderness, captivated by the festivities of a nearby tribe. Marlow follows in pursuit and attempts to get Kurtz’s attention: “I tried to break the spell—the heavy, mute spell of the wilderness—that seemed to draw him to its pitiless breast by the awakening of forgotten and brutal instincts, by the memory of gratified and monstrous passions.” Marlow indicates here that what he previously described as nature’s hidden, “implacable force” now has a hold on Kurtz. This force has caused Kurtz to cast aside all the trappings of civilized life and return to his primal, savage self. Marlow posits that this force has also driven Kurtz insane: “[H]is soul was mad. Being alone in the wilderness, it had looked within itself, and, by heavens! I tell you, it had gone mad.” Kurtz has stayed too long in the Congolese wilderness, which has resulted in the loss of his moral compass, his sanity, even his soul.

By the time Marlow stops talking at the end of the novella, it is clear that his tale, and perhaps his ominous use of nature symbolism, have had an effect on his audience. In the final sentence of Heart of Darkness, the frame narrator leaves the reader with this gloomy image of the River Thames: “The offing was barred by a black bank of clouds, and the tranquil waterway leading to the uttermost ends of the earth flowed sombre under an overcast sky—seemed to lead into the heart of an immense darkness.” At the beginning of the novella, the frame narrator complains that Marlow’s tales of his experiences are often “inconclusive.” However, the conclusion the frame narrator offers here proves similarly inconclusive. Indeed, his vague suggestion that the Thames leads “into the heart of an immense darkness” recalls the foreboding character of Marlow’s own language. In the end, then, the ominous use of nature in Heart of Darkness conjures a disconcerting and inconclusive sense of that which is unknowable.