In many respects, one of the basic themes of Conrad's work is the idea that within each human being exists a duality. There is a duality within Kurtz. On one hand, he is the well- educated and extremely refined European. On another hand, he is the brutal savage. "The horror" could very well refer to his own condition of duality. The impressions that one has of Kurtz reflects an eternal "struggle" as a result of this duality:
He struggled with himself, too. I saw it—I heard it. I saw the inconceivable mystery of a soul that knew no restraint, no faith, and no fear, yet struggling blindly with itself.
The idea of "struggling blindly with itself" is a significant aspect of the work's thematic development. Its resonance is a powerful one. In it, Conrad identifies an essential aspect of what it means to be human. Living with duality and its struggling becomes part of the human experience. It is this universality that makes the work's themes able to be seen in any setting. As a result, Conrad's work was able to be so easily adapted into the context of Vietnam in Coppola's Apocalypse Now. In this light, the setting could be changed and still be successful to the theme.
With this in mind, I think that it should be noted that the setting of the Congo enhances the meaning of the theme. The premise of what exactly "darkness" is becomes multi- dimensional with the presence of the African setting. Where is "the darkness" that lies in the base of "the horror?" At the same time, the setting of Africa enhances the "darkness" that lies within European imperialism. To change the setting take away from some of the meaning that is present. This results in a universality regarding the themes in the work. This universal applicability is not limited by the setting. However, it is clear to me that the setting adds so much more to the work and the themes within it. This is where the setting becomes important to the work as it helps to enhance the thematic purpose within Conrad's work.