The aim of this book is best served by beginning with a seemingly simple question: What is conservation biology? I do not pretend to be the first to have asked this question; however, I also do not think it is asked often enough by those who consider themselves conservation biologists. Michael Soule asked it in 1985, not long after conservation biology was formally recognized as a discipline. It seems his answer to this question has been deemed adequate by most, and the question has not been publicly asked much since. This indicates something of a reflective weakness for the discipline, which should be strengthened. Four decades have passed since the question was posed, and such a time span, moreover, should warrant its serious reexamination.