Newman says that his aim in the Apologia pro Vita Sua is not to present doctrine but to trace his own personal religious history. The most important Christian aspect of the work, therefore, is its autobiographical conversion story, which places it in the tradition of Saint Augustine’s Confessiones (397-400; Confessions, 1620) and John Bunyan’s Grace Abounding to the Chief of Sinners (1666), though in contrast to those works, Newman’s Apologia pro Vita Sua is not about a sinner wrestling with demons, but about a bookish man undergoing an intellectual crisis that causes him to shift from one church to another.
Newman does take up some doctrinal matters, however, notably the question of the infallibility of the Catholic Church. He argues that in a sinful world in which human reason can easily run amok and lead to skepticism, it is necessary to have a strong institution like the Catholic Church, which can issue infallible decrees in matters of faith and which must be obeyed on those matters and also on matters beyond faith.
However, Newman argues that this does not mean an end to free inquiry and private judgment; rather, he sees such inquiry flourishing in fruitful interaction with the infallible Church. He argues that Protestants are wrong to say that they have a monopoly on private judgment; he sees it as operating within the Catholic Church as well.
Newman also emphasizes the importance of unity or universality (what he sometimes calls “Catholicity”) within the Church. In the end, he decided that unity was so important that no error within the Catholic Church could have justified the Protestant Reformation, which he saw as introducing lawlessness and schism.
Another issue Newman deals with is the position of the Virgin Mary and the saints in the Catholic Church. For many years, this remained the main stumbling block keeping him from converting, because he feared that Catholic worship of Mary and the saints as intercessors with God was a deviation from true Christian teachings. However, he recounts that he eventually was reassured that despite popular misconceptions, Catholic doctrine did not allow anyone, even Mary, to intercede between individuals and God. For Newman, the individual soul must be able to connect directly with God, and he was satisfied that this view was consistent with Catholicism.