Catechisms represent the most basic and concise form of instruction in religious education. The doctrine presented in the catechism forms the foundation for theological development and sets a standard requirement for belonging in the faith community. In eighteenth-century New Spain, the most popular catechism was the Spanish Jesuit Gerónimo de Ripalda’s Catecismo de la doctrina christiana. Though available in the viceroyalty from the 1600s, by the next century Ripalda’s catechism reached the apogee of its popularity, used not only in catechesis but to teach reading in primary schools. This widespread use and popularity connected the catechism to a myriad of processes and people within New Spain, linking their experiences and involving virtually all of the viceregal institutions. The high regard held for Ripalda’s catechism makes it a privileged point of access from which to view and analyze eighteenth-century New Spain. In this thesis, I use Inquisition denuncias from the eighteenth-century to examine the responses of three groups towards Ripalda’s catechism in New Spain: the complainants of the denuncias, the Tribunal of Mexico, and the quotidian population. These denuncias focus on printing errors, Jesuit doctrine and attempts to replace Ripalda’s catechism. Behind these surface complaints, the denuncias give even richer detail, adding nuance to the context of the Bourbon Reforms, the Santo Oficio, the American printing industry, and what Indigenous and non-Indigenous education looked like in New Spain. Because of its widespread and favoured use, Ripalda’s catechism evolved into something much more than the contents of its religious doctrine. It became intertwined within the identity of the people of New Spain, crossing class lines, caste boundaries and cultural divides to become a point of connection within that society.