The Promoter of the Faith in Causes of Canonization is also known as the devil's advocate. The Promoter was created in order to safeguard the integrity of the Canon of Saints and was incorporated into the 1917 Code of Canon Law. This figure was transformed in the 1983 Code of Canon Law. This doctoral thesis studies the historical evolution of this figure as well as the corresponding rights and obligations in the various canonical norms. More information about this work can be found at www.jgray.org.