Thomas began his greatest undertaking by writing the Summa Theologica. He walked away from this work, leaving it unfinished, and began writing commentaries on many of Aristotle's writings. Thomas believed that Aristotle's ideas were important enough to be developed and clarified. As a philosopher, Thomas was “decidedly Aristotelian” (McInerny). The saint adopted many of his ideas from Aristotle and natural philosophy, as shown in the Summa Theologica where the theologian names the philosopher almost two hundred times (Aquinas). The Summa Theologica is divided into three main parts: the existence and nature of God, man and Christ. These topics are then divided into several subtopics. Saint Thomas shared his belief that religion and reason could coexist. In his writings, Saint Thomas proved that God's revelation is not contrary to reason. Thomas's Summa Theologica inspired numerous decrees of the Church. Thomas remains one of Christianity's most influential theologians and one of its most important philosophers. His works are unmatched by any other theologian and are always consulted when the Church makes a decision regarding the teachings of