In Joseph Conrad's "Heart of Darkness," the phrase "The horror! The horror!" encapsulates the protagonist's profound realization of the brutality and moral ambiguity present in humanity. As Marlow witnesses the atrocities of colonialism in the Congo, he grapples with the darkest aspects of human nature, leading him to a chilling epiphany about civilization and savagery. This quote serves as a haunting summation of his journey and the despair he feels about the inherent darkness within people.

The expression reflects not only Marlow's personal horror but also critiques the imperialist mindset of the time. Throughout the novella, Conrad explores themes of alienation, the duality of man, and the effects of colonization, ultimately suggesting that the true horror lies within and not just in the external world. This exploration challenges readers to confront the uncomfortable truths about their own existence and the consequences of human actions.