The Proslogion is a philosophical work written by Anselm of Canterbury in the late 11th century, primarily focused on the existence and nature of God. This text is crucial in the development of medieval philosophy and scholasticism, as it introduces the ontological argument for God's existence, emphasizing reason and faith as integral to understanding divine truth. Anselm's method of using rational inquiry to address theological questions laid the groundwork for future scholars and thinkers in the scholastic tradition.