Joseph Conrad's representation of Africans in Heart of Darkness has been the subject of much controversy. Critics have accused Conrad of racism in portraying the indigenous people of the Congo as passive, savage, silent, and lacking in agency.
Supporters of Conrad, on the other hand, have argued that in his depiction of Africans, he is actually laying bare the baleful effect of colonialism on the native population. If Africans are silent and passive, it's because of the condition to which they've been reduced by white Europeans.
Whatever the truth of the matter, there is no doubt that there is a huge difference between the representation of Africans and Europeans in the book. If Africans are largely passive, Europeans are active, men of action carving out a slice of Africa for financial gain. If Africans are silent, then the Europeans are vocal, monopolizing the words spoken in the story. And if Africans lack agency, white European colonialists are autonomous, able to do pretty much whatever they like now that they've conquered this part of the world.
One of the key differences between the respective portrayals of Africans and Europeans in Heart of Darkness concerns the use of language. Whereas the language of Europeans, especially Kurtz, can be quite lavish and grandiose, that of the indigenous Africans, in the few cases where they speak in the book, is terse and precise.
What Conrad appears to be driving at here is the way in which European colonialists use—or rather, abuse—language to cloak the essential exploitive, rapacious nature of the colonial project. Africans, on the other hand, being closer to nature, do not need to resort to such linguistic subterfuge in communicating their thoughts and feelings.