The influential philosopher who wrote *A Discourse on the Method* is René Descartes. This foundational text, published in 1637, explores the principles of rationalism and skepticism. Descartes famously stated, "I think, therefore I am," highlighting the importance of self-awareness and reasoning in philosophy. His work laid the groundwork for modern Western philosophy and greatly influenced subsequent thinkers. Through his emphasis on doubt and systematic thinking, Descartes initiated a shift towards a more scientific approach to understanding existence. His legacy endures in disciplines ranging from mathematics to psychology, marking him as a pivotal figure in the history of thought.