This work demonstrates how Pius IX combined the above elements in a unique way. As a major figure of his time he shepherded the Church along the path towards the 20th century. During an epoch marked by revolutions, he filled the religious vacuum among the people with a spirituality that was accessible to them.The first part of the book illustrates Pope Pius IX's devotion to Mary. It presents a description of certain people and events that shaped his life and demonstrates how he, in turn, influenced those around him. The second part examines his devotion to the Immaculate Conception. This section forms the centre of the study.After a thorough analysis of the events that led to the promulgation of the dogma, the author offers a history of the development of the Papal Bull defining the Immaculate Conception, as well as a presentation of the liturgy of the Immaculate Conception. Based on accurate scientific research, this study is able to offer the reader a profound insight into the time and personality of Pius IX.