The essays in this volume were written between 1985 and 1999, after I had recognized that my philosophical convictions had become those of a Thomistic Aristotelian, something that had initially surprised me. All of them give expression to that Thomistic Aristotelian standpoint, albeit in very different ways. The first four are concerned with the interpretation and defence of Aristotelian and Thomistic positions. The remaining eight contain only occasional references to Aristotle or Aquinas and sometimes none at all. Nonetheless each arrives at conclusions that are supportive of, derived from, or at least consistent with a Thomistic Aristotelian stance, even though in one case – that of the content of the rule forbidding the utterance of lies – my conclusion is at odds with Aquinas's own. The great majority of present and past Aristotelians are of course not Thomists. And some Thomists have been anxious to stress the extent of what they take to be the philosophical as well as the theological differences between Aquinas and Aristotle. It is therefore important to make the case for understanding Aristotle in a way that accords with Aquinas's interpretation and in so doing it is necessary to distinguish and defend Aristotle so understood from a number of rival Aristotles. The first two essays are a contribution to those tasks. In their original version they were delivered as the Brian O'Neil Memorial Lectures in the History of Philosophy for 1997/98 at the University of New Mexico and I am grateful to the faculty and students of that department for their critical and stimulating discussion.