In this discussion, Gary Hatfield, the Seibert Professor of Philosophy at the University of Pennsylvania and a foremost expert on Descartes' Meditations, dives deep into the intricacies of Cartesian thought. He juxtaposes Descartes' philosophy with Aristotelian views, revealing a seismic shift in knowledge and reality. Hatfield sheds light on Descartes' use of doubt and certainty, particularly in the famous 'Cogito, ergo sum.' The podcast also explores the profound influence of Descartes' work on metaphysics and natural science, encouraging further inquiry into philosophical ideas.