Machado de Assis's religion is a disputed subject: the most common reading sees him as a skeptic, but there are scholars who defend a strong presence of Catholicism in his life and work. The sources consulted do not allow one to pin down a faith or its absence.
On the Catholic side, biographies record his acquaintance, in youth, with a priest, Silveira Sarmento, identified by some biographers as his Latin teacher, and the Bible and Christian themes appear in chronicles and novels. The researcher Maria Eli de Queiroz, in the book Machado de Assis e a religião, gathered what she considers abundant proof that he was not an atheist.
On the side of skepticism, most critics and biographers saw him as a skeptic in the English style. His goddaughter, Francisca de Bastos Cordeiro, said that he refused confession and extreme unction, an account that fuels the controversy. In The Posthumous Memoirs of Brás Cubas, chapter CLVII, the philosopher Quincas Borba says that Humanitism "is to be also a religion," but that is a character's speech and the author's irony, not a belief of his. Studies such as that of Eunice Piazza Gai (2008) treat doubt and the suspension of judgment as marks of Machado's style.
On Clavis: The Posthumous Memoirs of Brás Cubas, Quincas Borba.