How do we make sense of the world? On what foundation do we consider something worthy, beautiful, true, or even real? This book explores the philosophical work of Merab Mamardashvili, a widely popular thinker during the Soviet era, yet unjustly unknown in Western philosophy. Drawing on his topological approach to epistemology, this book illustrates his journey into the elusive ground that shapes what becomes thinkable. This is the first full reconstruction of Mamardashvili’s thought. It makes visible key concepts developed across his lectures and writings, and presents them in relation to major Continental debates on foundation and difference.