Lectures on the Principal Doctrines and Practices of the Catholic Church, by Cardinal Nicholas Wiseman, is a foundational work explaining core Catholic beliefs (like the Trinity, Incarnation, sacraments, Church authority) and practices (like Mass, prayer, sacraments) for a 19th-century audience, often contrasting them with Protestant views, presenting a comprehensive defense and explanation of the Catholic faith from scripture and tradition. It serves as a significant historical text, preserving Catholic apologetics and theology in its original form.