Saint Thomas Aquinas (1225 – 1274), an Italian Catholic priest, is considered the Catholic Church's greatest theologian and philosopher. His philosophical thought was immensely influential for both the Roman Catholic Church and for Modern philosophy, which developed or opposed his ideas. Aquinas attempted to synthesize Aristotelian philosophy with the principles of Christianity in his best-known work <em>The Summa Theologica</em>. It was intended as the principal theological teaching of the Catholic Church and presented the reasoning for the existence of God, creation, Man, Man's purpose, Christ, the Sacraments and back to God.