In the letters contained in this book, David Bohm argues that the dominant formal, mathematical approach in physics is seriously flawed. In the 1950s and 60s, Bohm took a direction unheard of for a professor of theoretical physics: while still researching in physics, working among others with Yakir Aharanov and later Jeffrey Bub, he also spent time studying "metaphysics"-such as Hegel's dialectics and Indian panpsychism. 50 years on, questions raised about the direction and philosophical assumptions of theoretical physics show that Bohm's arguments still have contemporary relevance.