Continuing to talk about taking revenge, the underground man says that those who are able to do so act on impulse like a bull and only stop when faced with a wall of “morally decisive, definitive meaning.” He says that such a person is stupid, but he is envious of someone like this. By contrast, “a man of overly acute consciousness” thinks of himself as a mouse. Such a “mouse,” says the underground man, can feel malice and a desire for revenge, but has too many questions and doubts for it to take action. So, it retreats “ignominiously back into its mousehole.”
The underground man literally dehumanizes mankind by continually comparing people to animals, showing his low estimation of human character. His “overly acute consciousness” prevents him from acting on impulses and results in his isolation underground, comparable to the mouse’s retreat to its hole.
The underground man continues to describe the mouse in terms that seem to resemble his own life: retreating underground for years, it remembers its humiliation in an “abominable state of half-despair and half-belief,” in which there is nonetheless a “strange enjoyment.” He then returns to the subject of the men who act impulsively like bulls. He says they give up when faced with impossibility, which he describes as a stone wall that represents “the laws of nature, the conclusions of natural science and mathematics.” As an example, he mentions how people simply accept the fact that they are descended “from a monkey.”
Through the mouse, the underground man essentially describes his own situation in life: he is isolated from society and finds a “strange enjoyment” in his despair. He is annoyed by the certainties of “the conclusions of natural science and mathematics,” such as the Darwinian idea of evolution, which may contribute to the underground man’s idea of mankind as simply an animal, like any other.
According to the underground man, most people see the laws of nature and mathematics as inviolable, thinking it is impossible to protest, for example, that “two times two makes four.” He says that he is disgusted by the “impossibilities of stone walls,” represented by scientific fact and as a result sinks “voluptuously into inertia” and spite.
The simple equation “two times two makes four” represents the oppressive rationality that disgusts the underground man. He reacts to the certainties of reason and logic with spite, attempting to prove his free will through his ability to resist reason and natural laws.