Hilary of Poitiers begins his treatise De Trinitate with what appears to be an autobiographical narration of his journey to the Christian faith. Scholars, though taking different approaches to explain this narration, have overlooked its significance for Hilary's treatise. In the following essay, I argue that Book I is a reflection on sources of knowledge about God, the role of faith and reason in theological inquiry, the proper approach to scripture, and the soteriological context of any discussion on the mystery of God. These methodological reflections guide the reader through Hilary's treatise and make Book I crucial to understanding his purpose in De Trinitate.