"A Treatise on Relics" is an important work written by John Calvin, an outstanding reformer of the 16th century. In this book, the author analyzes the practices of the cult of relics in the medieval church, revealing their essence and influence on the Christian perception of faith. Calvin reveals the problems associated with the use of relics in religious rites and causes one to understand the essence of Christianity through simplicity and faith in the Word of God. This book became one of the key works in the formation of Protestant doctrine and contributed to the understanding of relics as a controversial aspect of religious practice.