Kirillov is the twenty-seven-year-old engineer who decides to kill himself to prove that he is God. The idea, which he received from Stavrogin and carried further than its owner, is this: if there is no God, self-will belongs to him, and the fullest point of that self-will is to kill oneself without fear and without reason.
He lives in a pavilion of Filippov's house, drinks tea at night, walking the room until dawn, and says he seeks to understand why people do not dare to kill themselves: two prejudices hold them back, pain and the other world. For him, "God is the pain of the fear of death," and whoever conquers the pain and the fear will be god. He also speaks of seconds when time stops and eternal harmony is felt, and of a man who is unhappy only because he does not know that he is happy.
He agrees to kill himself and to take on the crime Pyotr dictates, the murder of Shatov, because he says the act is only his will, not an agreement. On the night of his death, he explains: "I am obliged to kill myself," because that is the fullest point of his self-will; killing another would be the lowest point.
The doctrine is cold, but the scene is not. Kirillov laughs, scribbles a mocking note on paper, hides in a corner, bites Pyotr's finger, and fires only after shouting "now" about ten times. Albert Camus took him as the limit case of logical suicide, and that reading holds for the argument; the scene shows something else. In his farewell letter, Stavrogin says that Kirillov was magnanimous because he was not in his right mind.