I wrote this book as a way of saying goodbye. I first went to Cambridge on a Mellon Fellowship when I graduated from Yale in 1970, and with occasional excursions back to the United States I ended up staying there for almost twelve of the next fifteen years. Cambridge is in many ways my intellectual and emotional home: I had never seen before such a warm, supportive, yet challenging intellectual environment. Perhaps that is why I stayed so long. When I decided to return to the U.S. in 1985, I wanted somehow to mark, intellectually if not emotionally, the time I had spent in Cambridge. Most of my research on Aristotle was done while I was first a student and later a Fellow at Clare College, so I decided to write an introduction to his philosophy. I liked the idea of an introduction, first, because I thought it would force me to work on a broad canvas: to elucidate the thoughts of years rather than detail a single argument. Second, I wanted to write a book that was accessible to my friends who are not Aristotelian scholars – friends who would ask me in countless casual conversations, ‘What do you think Aristotle would have thought about this?’ I am not going to mention my many Cambridge friends by name: if you are one of them and are reading this, suffice it to say that you are very much in my heart and mind.