Newton's bucket, Einstein's elevator, Schro?dinger's cat - these are some of the best-known examples of thought experiments in the natural sciences. But what function do these experiments perform? Are they really experiments at all? Can they help us gain a greater understanding of the natural world? How is it possible that we can learn new things just by thinking? In this revised and updated new edition of his classic text The Laboratory of the Mind, James Robert Brown continues to defend apriorism in the physical world. This edition features two new chapters, one on "coun