Symbols are objects, characters, figures, or colors used to represent abstract ideas or concepts.
Fog is a sort of corollary to darkness. Fog not only obscures but distorts: it gives one just enough information to begin making decisions but no way to judge the accuracy of that information, which often ends up being wrong. Marlow’s steamer is caught in the fog, meaning that he has no idea where he’s going and no idea whether peril or open water lies ahead.
The “whited sepulchre” is probably Brussels, where the Company’s headquarters are located. A sepulchre implies death and confinement, and indeed Europe is the origin of the colonial enterprises that bring death to white men and to their colonial subjects; it is also governed by a set of reified social principles that both enable cruelty, dehumanization, and evil and prohibit change. The phrase “whited sepulchre” comes from the biblical Book of Matthew. In the passage, Matthew describes “whited sepulchres” as something beautiful on the outside but containing horrors within (the bodies of the dead); thus, the image is appropriate for Brussels, given the hypocritical Belgian rhetoric about imperialism’s civilizing mission. (Belgian colonies, particularly the Congo, were notorious for the violence perpetuated against the natives.)
Both Kurtz’s Intended and his African mistress function as blank slates upon which the values and the wealth of their respective societies can be displayed. Marlow frequently claims that women are the keepers of naïve illusions; although this sounds condemnatory, such a role is in fact crucial, as these naïve illusions are at the root of the social fictions that justify economic enterprise and colonial expansion. In return, the women are the beneficiaries of much of the resulting wealth, and they become objects upon which men can display their own success and status.
The Congo River is the key to Africa for Europeans. It allows them access to the center of the continent without having to physically cross it; in other words, it allows the white man to remain always separate or outside. Africa is thus reduced to a series of two-dimensional scenes that flash by Marlow’s steamer as he travels upriver. The river also seems to want to expel Europeans from Africa altogether: its current makes travel upriver slow and difficult, but the flow of water makes travel downriver, back toward “civilization,” rapid and seemingly inevitable. Marlow’s struggles with the river as he travels upstream toward Kurtz reflect his struggles to understand the situation in which he has found himself. The ease with which he journeys back downstream, on the other hand, mirrors his acquiescence to Kurtz and his “choice of nightmares.”