During medieval times (500–1350) philosophers concerned themselves with applying the works of ancient Greek thinkers, such as Aristotle (384–322 B.C.) and Plato (c. 428–347 B.C.), to Christian thought. This movement, which spanned most of the Middle Ages and reached its high-water mark in the thirteenth century, was called Scholasticism since its proponents were often associated with universities: the word scholastic is derived from the Greek scholastikos, meaning “to keep a school.” In the simplest terms, the goal of Scholasticism has been described as “the Christianization of Aristotle.” Indeed, medieval philosophers strived to use reason to better understand faith. Scholasticism was, therefore, both rational and religious. The movement was also an interesting occasion of East meets West: The commentaries of Islamic philosophers, principally Avennasar (c. 878–950), Averroës (1126–1198), and Avicenna (980–1037), figured prominently in Scholasticism. Theologians, including St. Anselm and St. Thomas Aquinas, used the non-Christian philosophy—both of the ancient Greeks and of Muslim thinkers—to better understand their own Christian faith.