In the classic novel, Heart of Darkness, Joseph Conrad takes us on a journey into the soul of man. When the character of Marlow travels into the Congo of Africa to find Kurtz, he realizes that he is in a place where the rules of society no longer constrain human nature, and the frightening truths about human beings can be observed first hand.
Marlow discovers that human nature can experience its' dark side. This can be seen through the observation of Kurtz. He also discovers that human nature can be altered, subject to the constraints placed on it by the environment, and that it is able to be either good or evil. The temptation of evil, existing especially in an environment lacking any rules, creates turmoil in the human soul, as it struggles between its conscience and its tendencies towards evil. Kurtz confides in Marlow near the end of the book, and from him Marlow learns about human nature as he examines Kurtz's destroyed soul.
Marlow says, "By being alone in the wilderness, it had looked within itself, and....it had gone mad "(146). Marlow observes how Kurtz struggles with himself, and the horrors of the wilderness that he had given in to.
Furthermore, when Marlow arrives at Kurtz's station, he finds that Kurtz participates in horrible ceremonies, such as the practice of placing beheaded natives' heads on fence posts. Marlow believes that the wilderness "whispered to him things about himself which he did not know, things of which he had no conception till he took counsel with this great solitude -- and the whisper had proved irresistibly fascinating" (133). Without the restrictions of people, Kurtz is able to fulfill his inner desires and go beyond any restrictions that he may have had before. In Kurtz, Marlow sees "the inconceivable mystery of a soul that knew no restraint, no faith, and no fear, yet struggling blindly with itself" (144). As Kurtz approaches death, he struggles desperately with himself and the evil that he had resigned his soul too. "Both the diabolic love and the unearthly hate of the mysteries it had penetrated fought for the possession of that soul satiated with primitive emotions, avid of lying fame, of sham distinction, of all the appearances of success and power"(146).
The conflict between good and evil is raging in Kurtz's soul at this time, as he struggles between the greatness that he had possessed, and the emptiness of a soul tempted by evil. When first talking to Marlow, Kurtz tells him that he was "on the threshold of great things" (143). As they travel through the wilderness to leave the station that destroyed Kurtz, Marlow comments, "Oh he struggled! He struggled! The wastes of his weary brain were haunted by shadowy images now -- images of wealth and fame revolving obsequiously round his inextinguishable gift of noble and lofty expression" (146). Even as he waits to die, Kurtz's greatness refused to completely submit as it fights the powerful force of evil that has consumed his soul. Before he dies, Marlow observes on Kurtz's face "the expression of somber pride, of ruthless power, of craven terror"(147). All of human nature, evoked from the lack of limitations he found in the wilderness, fought within him until the end - when he sums up his struggles and observations of human nature with one phrase: "The horror! The horror!" Marlow admires Kurtz for these words, because Kurtz had learned and reached a conclusion on human nature in his last moment of life, and, as Marlow says, "the most you can learn from it is some knowledge of yourself...." (148). Marlow also calls these words "a moral victory" because they show that he had struggled to the end. Hence, Kurtz has not simply resigned to a state between good and evil, but he has been able to judge everything that he had experienced, throwing out one phrase at the end of his struggle that summed up human nature.
This ability was Kurtz's greatness. His last words had "the appalling face of a glimpsed truth -- the strange commingling of desire and hate" (149). "The horror" that Kurtz labels is the struggle between good and evil that a great man experienced when faced with human nature in its purest form, without the social order's constrictions.
After Kurtz's death, Marlow takes with him the knowledge of human nature that he gains from him. Kurtz, the ideal European, full of accomplishments, deteriorates from his previous character when left in the uncontrolled Congo. He says, "I remembered his abject pleading, his abject threats, the colossal scale of his vile desires, the meanness, the torment, the tempestuous anguish of his soul" (153). Marlow sees his face in windows, and hears his last words everywhere. He is haunted by the tormented discoveries that Kurtz passed on to him, and when he confronts Kurtz's intended, who is a symbol of good, he is not able to corrupt her goodness by rendering Kurtz the justice of passing on his words to others. Although he feels that he has betrayed Kurtz, he still does not feel that he is able to pass on his judgement because "It would have been too dark -- too dark altogether..." (157). Instead, Marlow retains the truth of human nature within himself, mourning the terrible and traumatic end of the great man that Kurtz was, and continued to be, in his mind. Kurtz was great because he answers the question of human nature that haunts everyone. He found truth and fought the battle of good and evil, and in the end was still able to judge himself with his own harsh words: "The horror!" One is truly able to see this internal struggle in Joseph Conrad's Heart of Darkness, as Kurtz struggles between his conscience and his tendencies towards evil.