John Cottingham is one of the world’s leading scholars of René Descartes and early modern philosophy. He is Professor Emeritus of Philosophy at the University of Reading and the author of several influential books on Descartes, ethics, and philosophy of religion. Cottingham is also widely known for his work on the Cambridge Edition of the Works of Descartes, where he served as editor and translator, helping shape how Descartes is read and understood today. In this episode, we explore Descartes’ philosophy from its foundations to its modern consequences. We discuss the method of radical doubt, the meaning of “I think, therefore I am,” the mind–body problem, and why consciousness still resists purely scientific explanation. We also examine the central role God plays in Descartes’ system, whether reason alone can justify belief, and how these ideas continue to shape debates in philosophy, science, and artificial intelligence today.