Passage/lines from the text:
“I want you to understand that there was nothing exactly profitable in these heads being there. They only showed that Mr. Kurtz lacked restraint in the gratification of his various lusts, that there was something wanting in him-some small matter which, when the pressing need arose, could not be found under his magnificent eloquence.”
“Direct-Connect” to the storyline/plot:
This quote displays the opinion that Kurtz’s own world, in which darkness rages, is not controlled by method or reason, but really by impulse and lusts. Cutting people’s heads off had no real purpose for Kurtz and the other villagers except that it satisfied his dark needs. This probably aided in the upkeep of his god like image to the natives. Normal individuals would not have simply cut off the heads of people because they felt like it.
This quote ties into the impulse that described in murderers. Murderers describe a feeling of impulse that they have never experienced before when they end up killing someone. People who go on killing sprees exhibit these same qualities, being able to control themselves except for when an urge comes on and they viciously murder someone. People exhibit these traits of inescapable darkness in the real word as Kurtz does in Heart of Darkness.
I have experienced times of rage, but not in the magnitude to kill someone. They are simply when someone angers me so much that I feel that I must act and stop it.