The topic of this master's thesis explores the philosophical contributions of two great thinkers, Aristotle and Saint Thomas Aquinas, in relation to questions about the nature of the world, its eternity, the first cause, causality, and motion. The work is based on an analysis of their philosophical views and original writings to investigate different perspectives on these key topics. Aristotle's philosophy provides profound insights into the nature of the world, particularly through his consideration of motion, causality, and eternity. His concept of the Unmoved Mover plays a crucial role as the cause of all changes in the world, and discussions also revolve around the eternity of the world and its beginning and end. Following Aristotle, Thomas Aquinas introduces a new perspective in medieval philosophy by exploring the existence of God and His role in the creation of the world. His arguments for the existence of God and the concept of God's action as creation lay the foundation for a theistic understanding of the world. Through a thorough examination of relevant literature and the original writings of these two philosophers, this thesis explores their different perspectives on questions of the world's eternity and its causes, contributing to a deeper understanding of these profound philosophical themes. By analyzing Aristotle's concepts of motion, causality, and eternity in addition to Thomas's views on the nature of the world and God's actions, the thesis provides a deeper insight into the topics under consideration.