Conrad's usage of light and dark symbolizes, among many other things, enlightenment and despair. As Marlow travels further up the river, he becomes increasingly “cut off from the comprehension of surroundings .” The wilderness grows darker, and nothing connects him back to the civilized and familiar. Keenan's “Diaries of a Madman” states that, “Whenever I'm alone/voices in the darkness/scream away mental health [Diaries of a Madman, lines 17-19],” expressing how the solitude of the darkness drives away rationale, as it does in the novel. In another song Keenan speaks about a flood, an uncontrollable natural disaster, as overwhelming and chaotic. “All I knew and all I believed/Are crumbling images/that no longer comfort me/Scramble to reach higher ground/Order and sanity/or something to comfort me [Flood, lines 2-7].” The familiar disappears and cannot be rediscovered. Instead, “the truth has come to punish [line 22].” As in Heart of Darkness unfathomable amounts of water lead to insanity, but also to the hidden truth that “alone in the wilderness… [there is] no restraint, no faith, and no fear ,” only pure, savage emotions that lack reason.

Conrad often describes the forest as impenetrable and the river as immense, especially in comparison to the life of man. Marlow describes the forest and river as “expectant, mute, while the man jabbered about himself. I wondered whether the stillness on the face of immensity…was meant as an appeal or a menace .” An individual's “little existence ” will never be remembered throughout the ages; however, nature, in its enormity, will not be conquered and forgotten. Keenan, too, realizes his irrelevance in comparison to “cold, black, endless waters/…deep and rich like silt on a riverbed [Undertow, lines 3 & 6],” describing himself as “weak and numb and insignificant .” However, in another song the moon's infinite light saves him from the darkness, which differs from Marlow, who only receives more obscurity in his moments of need. Keenan writes that, “In darkest moment, fetal and weeping/The moon tells a secret/…Its source is bright and endless/She resuscitates the hopeless [Reflection, lines 10-11 & 14-15].” In this case the infinite power of nature relieves the mind of man, rather than causing feelings “so hopeless and so dark…so pitiless to human weakness .”

Conrad uses the character Kurtz as a representation of the plunge into insanity. When left alone, “Kurtz lacked restraint in the gratification of various lusts… and the whisper had proved irresistibly fascinating. It echoed loudly within him because he was hollow to the core .” Kurtz's desire for ivory and wealth leads to a search for ultimate power, and, when left without order, his morals vanish. Correspondingly, Keenan writes about a hollow, emotionless individual: “Run, desire, run him like a blade/to and through the heart/No conscious/One motive/…grow, libido, grow [Hollow, lines 1-4 & 11].” The hunger for sexual power runs his life until it cuts through his heart. Kurtz, “an animated image of death ,” also does not possess a working heart because his ego destroys it. Living with the natives for so long tears Kurtz's morals away, leaving no grounds for sanity or reality. However, because of his superior education and the natives' need of direction, they see him as strong, making him “one of the immortals .” The darkness of the jungle causes the natives “to be deaf and blind to anything but heavenly sights and sounds ,” which they find in Kurtz. This reflects Keenan's general words about religion that, “Choices always were a problem for you/what you need is someone strong to guide you./Deaf and blind and dumb and born to follow/…Just do everything I tell you to do/I want to rape you [Opiate, lines 1-3 & 10-11].” Kurtz recognizes the simplicity of the natives and takes the leadership role. Although the people believe he has pure intentions and, therefore, treat him like a god, he wants to rape them of their ivory and customs.

The lyrics of Maynard James Keenan's “Third Eye” reflect many themes present in Heart of Darkness by utilizing a contrast of light and dark as well as old and new. One song version opens with a sample from Timothy Leary, whose words also exhibit several themes of the novel. Conrad believes that, “inner truth is hidden ,” which Leary describes as “the frightening, terrorizing fact that we do not know who we are [Third Eye, line 4].” However, for Conrad finding the inner truth becomes the terror, since the true nature of human kind is malevolent. Leary continues by stating that, “the authorities…attempted to conform us by giving us order, rules, regulations [lines 6-7].” Conrad also expresses this theme when describing London “…
The epic portion of “Third Eye” describes the psychedelic journey into regions of the mind not accessed for years. The drug-induced state causes an expansion into the subconscious mind, awaking hidden thoughts and truths, similar to the Russian's description of Kurtz as a man who, “enlarged my mind …he made me see things .” During the trip the narrator, presumably Keenan, enters a dream-state where a “bright…shimmering [line 18]” face greets him with a smile and comforts him with “three warm and wild eyes [line 20].” The face represents his childhood self, who, like the natives, has “wild glances .” Although the face of the child exists in the light, the memory resides in darker regions of the mind as the natives reside in “the darkness of an impenetrable night .” Like the face in Kurtz's painting, “no manipulation of light and pose could have conveyed the delicate shade of truthfulness upon those features ” like on the child's face; truth flows from children since they lack the corruption of civilization. Continuing further on the trip, Keenan falls “down that hole [line 22]” in his mind, “wiping the webs and the dew from withered eye [line 24].” He struggles to return to an ancient place in his mind as Marlow struggles to reach an ancient place of the world, an area untouched by civilization. Keenan also reaches this place since his inner child remains unscathed by the conformity of the civilized. The child, like the natives, inhabits a dark territory that manifests certain desirability.

Keenan spends “years in question [line 27]” during his adulthood, deciding whether or not rules and conformity make sense, only to disobey the laws through drug-use. This creates an “awakening of forgotten and brutal instincts, by the memory of gratified… passions ,” that Kurtz encounters when alone in the wilderness. Kurtz and Keenan both experience a loss of morals; however, Kurtz degenerates to greed, while Keenan regresses to the purity and simplicity of childhood. Keenan continues by speaking to his inner child; “So good to see you/I've missed you so much/So glad it's over [lines 29-31].” He rejoices due to his rediscovery of the open-mindedness of youth and his abandonment of conformity. However, he then asks the child, “Why are you running [line 34]?” The child is afraid of what he has become, similar to how Marlow begins to fear that which he seeks. Although Marlow seeks Kurtz out of interest, he later describes him as, “a shadow insatiable of splendid appearances, of frightful realities; a shadow darker than the shadow of night .”

Keenan continues on the trip, becoming more descriptive and abstract. He describes his surroundings as “black as holes within a memory/and blue as our new second sun [lines 37-38].” His memories are black, therefore making his past primitive, while he compares the new with the sun. Unlike Heart of Darkness, Keenan illuminates the darkness by renewing his morals. He “sticks hand into the shadow [line 39]” in order to reassemble his childhood self, hoping for the creation of a new future based on the simplicity of childhood integrity. He recognizes this new self and again rejoices. However, the entire journey to reconnect with his past reveals an inner conflict, since he tries “prying open third eye .” His path to enlightenment shows struggle, needing to pry open his visions of a better self. Like Heart of Darkness, opening the third eye may reveal “the appalling face of a glimpsed truth ,” that no one wants to see. Since Keenan discovers childhood as pure and innocent, his truth does not prove frightening. However, on Marlow's journey the discovery of truth is “like a passage through some inconceivable world that had no hope in it and no desire .” Keenan's childhood self then speaks to him, divulging the fact that the adult had run away “chasing the tail of dogma [line 57]/…and reason [line 62].” As an adult, laws and reason govern his life, while the child lives through freedom. Youth possesses “the absolutely pure, uncalculating, unpractical spirit of adventure ,” that adults often forget. Kurtz lives “his life…in every detail of desire
The civilized population creates a mask of morals to hide its true self. When lifting the mask, one finds either a frightened but innocent child hiding in the dark, as Keenan did, or the untamed savage that performs sacrifices and dances in the impenetrable darkness, as conveyed by Conrad. Either truth is unseen, however, since it remains in the darkness until one peers over the edge for a momentary glimpse of reality. Although in both cases either drugs or mental instability blurs the so-called reality, the journey to the other side of consciousness provides a profound vision of existence. “All the wisdom, and all truth, and all sincerity, are just compressed into that inappreciable moment of time in which we step over the threshold of the invisible .”