"The focus of this book is on evaluation theory rather than on practice, even though we do suggest implications for practice. We believe theory is used to justify and inform practice, so the theory makes a difference to practice over the long run. And practice can inform theory, as it has done many times in the past. But, again, our focus is on reconciling evaluation theory with philosophy, which means this is not a how-to-do-it book. Rather, it is a book that develops middle-range evaluation theory consistent with contemporary thinking in philosophy (albeit a particular strand), especially thinking about democracy. A middle-range theory would suggest some attributes that evaluations should have, without necessarily specifying how to achieve them in particular cases. So the book offers a perspective about evaluation rather than a model of how to do evaluation." (Preface, page x)