This Volume I opens the collection: GOD IN HIS WORK OF LOVE with a complete study of the Catholic Faith in six volumes. Volume I is divided in THREE PARTS. PART ONE studies faith. First of all, in a detail presentation, we study the definition of faith as a knowledge we acquire through a witness. This leads us to study the TWO CLASSES of faith. This study is the most importan in the life of the believer. The beliver learns that faith is HUMAN or DIVINE. The human faith is most commonly used in day to day life of the believer even in church services. Unfortunately, the human faith is complely ignored in the CATECHISM OF THE CATHOLIC CHURCH. Definitely it is a serious mistake which someday will be corrected. The believer must understand what makes faith to be human and therefore has no power to save, and what makes faith to be divine. DIVINE FAITH is the only one that has the power to save. The SECOND PART studies God in his creation of the universe, the angels and Adam and Eve in their state of innocence. The THIRD PART studies Adam and Eve put to test since they had to merit heaven like the angels. Thus, God gave our first parents an order, they were not to eat the fruits from one specific tree. Adam and Eve were created with complete liberty to fulfill God's Will or to refuse salvation. Under the influence of the devil, our first parents opted to rebel against God; they refused to recognize and to worship God's complete dominion over his creation. They were convinced they could free themselves from God. The downfall of our first parents brought the whole human race with them in the state of sin. The original sin is specifically studied in each human born as descendents of our first parents Adam and Eve. The THIRD PART terminates Volume I with the Promise of the Redeemer. The Professor.