Our view is that debugging is an essential part of the craft of software development. By thinking of debugging as a primary endeavor, developers are liberated to be more rigorous about it and can afford the luxury of complete understanding. By considering debugging as opportunity rather than setback, developers can take a craftsman's pleasure in it, mastering its nuances and deriving intrinsic satisfaction from doing it well. This is the thesis of this book: that debugging must be rigorous and empirical -- but that within that rigor, software engineers can discover a joy unique in the craft.