Nancy Cartwright has been a dominant figure in the philosophy of science for more than twenty years. In the early eighties she wrote her influential book "How the Laws of Physics Lie" which was generally perceived to be a challenge to a realistic conception of scientific theories. Over the last decade her focus has shifted to issues concerning what she calls "fundamentalism". This is the position that laws of nature are basic and that other things come from them. Cartwright rejects this story and replaces it by the view that capacities are basic and that laws obtain "on account of the repeated Operation of a system of components with stable capacities in particularly fortunate circumstances". This book focuses mainly on Cartwright's recent work on laws and capacities. It is the outcome of the second series of the Münster lectures in philosophy which took place during 5 - 6 May, 1998. This volume comprises a revised version of Cartwright's evening talk, 12 colloquium papers which Cartwright considered to be "extremely thought provoking", followed by replies Cartwright makes to each of them.