Humanitism is the doctrine of Quincas Borba, the schoolmate of Brás Cubas who returns as a beggar and then as an heir. The name comes from Humanitas, "the principle of things", which the doctrine defines as "the same man divided among all men".
Quincas expounds the system to Brás at the table, between the chicken and the coffee, and days later reads him the four manuscript volumes. From them Brás takes that man, at once vehicle, coachman, and passenger, must worship himself; that war, hunger, and crime are necessary functions; that envy is a virtue, being an admiration that fights; that pain is pure illusion; and that there is only one misfortune: not to be born. The lunch chicken enters the demonstration as the result of a multitude of efforts and struggles. In the end, the philosopher closes the volumes by defending Pangloss, the optimist whom Voltaire ridiculed.
The doctrinaire applies the thesis to what happens. When Nhã-loló, Brás's fiancée, dies of yellow fever, Quincas explains that epidemics serve the species. Before two dogs fighting over a bare bone, he stops in ecstasy: "Life is struggle." Brás uses Humanitism as a tool of the moment: he baptizes a kiss with it, bases on it the program of a newspaper, and sends it to the devil when the doctrine wounds the pain he feels. Quincas himself ends up mad, aware that he is mad, and dies repeating that pain is an illusion.
The book does not discuss Humanitism as philosophy: it shows who uses it and to whom it is convenient. The procedure is always the same, renaming what is condemned until it fits among the virtues. In the next novel, Quincas Borba, the principle is taken up again, and Rubião, the philosopher's heir, receives the doctrine and repeats it after his death.