In order to discuss the theme of imperialism in Joseph Conrad's Heart of Darkness, it is important to do some investigating into the definition of the term. According to Encyclopedia Britannica, imperialism is defined as

state policy, practice, or advocacy of extending power and dominion, especially by direct territorial acquisition or by gaining political and economic control over other areas.

In other words, imperialism describes a situation in which a more powerful country takes over a less powerful country's resources in order to gain additional power for themselves. The theme of imperialism is a major point of discussion in Conrad's novel.

In the novel, the main character describes some of the major implications of imperialism and, in doing so, provides us with one of the most notable critique's of the subject. At one point, Mr. Kurtz is described as a "very remarkable person" who "sends in as much ivory as all the others put together." Not only is Kurtz noted for his ability to bring in more ivory than all the other entities combined, but it is for this very reason that he is pointed out as a "remarkable person."

However, the praise of Kurtz is heavily contrasted with a detailed depiction of the reality of the Congo. Conrad uses dark and violent imagery to describe the main character's surroundings. He writes,

A caravan had come in. A violent babble of uncouth sounds burst out on the other side of the planks.

It is explained that "the population had cleared out a long time ago," making it evident that the Europeans are not welcome in the Congo.

One important thing to note is the use of the word ivory in the text: the commodity is glorified and becomes a symbol of economic freedom and social advancement for Europeans. Conrad writes,

The word "ivory" rang in the air, was whispered, was sighed. You would think they were praying to it.

Conrad's vivid depiction of ivory is crucial; at the time, it was emblematic as a resource taken from a less developed country by a more developed one to benefit themselves—at the expense of morals and ethics. The main character continues to say,

I've never seen anything so unreal in my life. And outside, the silent wilderness surrounding this cleared speck on the earth struck me as something great and invincible, like evil or truth, waiting patiently for the passing away of this fantastic invasion.

The speaker's imagery suggests Conrad's criticism of imperialism. In the quote, the main character describes his surroundings as a "fantastic invasion" and conveys the weight of the situation to his audience by using words like "evil or truth" in the same context as "great and invincible."

Toward the end of the novel, the speaker describes the natives as they

stamped their feet, nodded their horned heads, swayed their scarlet bodies; they shook towards the fierce river-demon a bunch of black feathers, a mangy skin with a pendent tail—something that looked like a dried gourd.

The main character continues to describe the natives as

they shouted periodically together strings of amazing words that resembled no sounds of human language; and the deep murmurs of the crowd, interrupted suddenly, were like the responses of some satanic litany.

By depicting the main character's perspective of the natives so transparently and with such vivid imagery, Conrad puts forth his honest critique of imperialism. Particularly, he describes the landscape and the natives as "foreign" to his own culture and surroundings. In this way, the locals' behaviors and practices are depicted as "responses of some satanic litany."

This description is significant to the theme of imperialism because Conrad is heavily emphasizing just how unfamiliar the Congo is from the main character's usual surroundings. The descriptive journey into the "heart of imperialism" is significant because it represents the perspective of many Europeans who benefited from imperialism.

In conclusion, the novel is a deeply effective device for compelling its audience to acknowledge the reality of imperialism, largely due to its ability to put the reader in the perspective of an individual witnessing such an unfathomable situation in a faraway land for the first time, as well as the main character's inability to escape from the limitations of his perspective.

Joseph Conrad’s Heart of Darkness tells the story of an Englishman named Marlowe who travels to the African continent and encounters a deeply troubling situation as he searches for another Englishman named Kurtz. Kurtz works for a company that is extracting ivory from Africa.

It is the negative aspects of commercial colonialism/imperialism that make the novel’s theme troubling. As Marlowe travels up the river on his way to Kurtz’s station, Conrad describes the condition of the indigenous inhabitants that Marlow encounters. In many cases, these inhabitants are sick, listless, and dying for reasons that Marlow does not specify. Conrad’s point here is to show the destructive effect of English imperialism—it destroys the lives of many Africans. We can deduce that the white men have brought disease that the Africans have not developed an immunity to. They have also forced some of them into labor against their will.

The Africans also affect the white men negatively. The white men often live in fear of their surroundings and the Africans they have subjugated. Thus Conrad describes an imperialistic situation in which both sides suffer. The only winner is the company that profits from the ivory, but it headquartered safely in Europe, far from the devastation it has caused.

Corporate imperialism and commercial colonization are the twin forces that stand behind all the action of the novel. It is in the interest of business that Marlow and Kurtz both come to the Congo.

They take part in a violent and (somewhat) organized form of exploitation and pillaging, working for a company that hauls ivory out of Africa, exploiting the local population as a labor force and destroying the local ecology.

Claiming to educate the natives, to bring them religion and a better way of life, European colonizers remained to starve, mutilate, and murder the indigenous population for profit.

Imperialism of this type is rather roundly condemned by Marlow in the narrative, yet it remains the driving force behind his journey, following Kurtz, into the heart of the jungle and into moral chaos.

This division between belief and action borders on hypocrisy and characterizes many of the characters working for the Company, Marlow and Kurtz included. 

Hypocrisy is a salient theme in Heart of Darkness. Marlow's account repeatedly highlights the utter lack of congruence between the Company's rhetoric about ‘‘enlightening’’ the natives with its actual aims of extracting ivory, minerals and other valued commodities.

Extending the discussion of hypocrisy and self-conflict to Kurtz, we need only point to the notebook entry Marlow discovers where Kurtz outlines his desire to help improve conditions for the native Africans. At the end of the journal entry, a statement is scrawled across the page, reading, "Exterminate the brutes."

Kurtz wants to help alleviate the damage of the commercial project he is a part of. He also wants to wipe out the native population. 

This schism in Kurtz is reflected in the distance between the Company's stated goals in Africa and its actual treatment of the population. 

Ultimately, the novel's commentary made on imperialism is clearly and strongly negative, condemning the nameless corporate men running the Company in Belgium as well as the agents of the Company working in Africa. Though Marlow cannot be simply extracted or exonerated from his role as an employee of the Company, his view are distinctly set against any belief that the Company is doing humane work in Africa. He is, then, against the project of commercial colonialism and the larger projects of imperialism.

Marlow, both as narrator and as a character, stands apart from the culture and actions that he witnesses. He does not belong to the Company, does not believe in its imperialist work, and does not blithely accept or represent it as its other agents do. 

The Central Station manager says to Marlow, ‘‘you are of the new gang—the gang of virtue."