René Descartes, a French philosopher and mathematician of the early 17th century, is often referred to as the father of modern Western philosophy. His influence extends beyond the realm of abstract thought; it has shaped various dimensions of moral philosophy, and his ideas still resonate in contemporary ethical discussions. Descartes is particularly notable for his method of systematic doubt, his emphasis on reason as the path to knowledge, and his quest to establish a foundation for the sciences grounded in certainty.

Among his central works, "Meditations on First Philosophy" stands as a cornerstone of his philosophical legacy. Written in 1641, this text delves into epistemology—the study of knowledge—and introduces the famous declaration, "Cogito, ergo sum," or "I think, therefore I am." This assertion encapsulates Descartes’ approach to understanding existence and the mind. Through systematic doubt, Descartes sought to strip away all uncertain beliefs until he reached something indubitable—a foundation upon which knowledge could be built. This inquiry into doubt leads us into the heart of his moral philosophy.

In moral philosophy, Descartes is renowned for coupling his rationalist approach with notions of free will and moral agency. He posits that morality is closely associated with human reason. For Descartes, an action is morally right if it is aligned with the dictates of reason; this places reason as the guiding principle for ethics. In doing so, he distinguishes between the passions, or emotions, which can mislead us, and the rational will, which, when exercised correctly, leads us toward ethical actions. For someone navigating the complexities of modern life, this framework encourages a reflective approach to decision-making that takes into account reason over impulsive feelings.