Trappist is the order of Catholic monks Merton decides to join. The word, he explains, originates from the idea of silence, which is a practice Trappist monks are committed to. While Merton was happy to try and join other sects of Catholicism for the sake of becoming a priest, none of them resonated with him the way Trappism did: not because it felt easy but because it would be hard work, and that felt right to him. The Trappist monasteries mentioned in the book are in Kentucky and Canada.

While Merton grapples with the meaning of Catholicism and juxtaposes it to Protestantism and Quakerism, there isn’t a coherent definition of Catholic in the work. Rather, Merton’s Catholicism is the sect of Christianity that draws him in because of its traditions and focus on God rather than the lives and outfits of other members of the church. He prods into the differences between Augustinian Catholics and so forth, especially toward the end, wondering how much of a contemplative life is possible and ideal.

Merton takes the time to dwell on the concept of God, introducing a related concept that he thinks even Christians don’t understand: the idea of aseity. He writes: