Commonitorium has long been felt by students of Patristic Literature. Translations there are in plenty, but no edition of any critical value has ever been published in this country. The present is an attempt to supply the want. The importance of this treatise in regard to the question of Tradition, the permanent value of the Rule of Vincentius, and the prominent part played in controversy both ancient and recent by his famous definition of orthodoxy, all combine to place this work in a somewhat different position from that occupied by other writings of a similar nature. It has been variously called 'a masterpiece of theo Iogical reasoning,' 'a monument of faith,' 'a golden book,' 'a work small in size but great in Virtue.' Its doctrinal value has never been seriously disputed and particularly now is it held in high esteem, inasmuch as there is an increasing tendency in various schools of modern religious thought to go back to the primary truths of Christianity which make up the Catholic Faith.