The first rationalist we will cover is Rene Descartes. Descartes details his methodical approach to doubting established beliefs, aiming to construct a firm foundation for truth. The excerpt covers his skepticism, his four maxims for reasoning, and his proofs for the existence of God and the human soul. Further, it summarizes his physics, focusing on the motion of the heart and the distinction between humans and animals. Finally, it discusses the reasons behind his decision to publish his work, expressing both confidence in his methods and reluctance to engage in fruitless controversies.