What is the history of philosophy? Is it history or is it philosophy or is it by some strange alchemy a confluence of the two? The contributors to the present volume of essays have tackled this seemingly simple, but in reality difficult and controversial, question, by drawing on their specialised knowledge of the surviving texts of leading ancient philosophers, from the Presocratics to Augustine, through Plato, Aristotle and Plotinus. These contributions, which reflect the range of methods and approaches currently used in the study of ancient texts, are offered as a tribute to the scholarship of Denis O'Brien, one of the most original and penetrating students of the thousand-year period of intense philosophical activity that constitutes ancient philosophy. Contributors include: T. Ebert, F. Fronterrota, C.J. Gill, C. Huffman, N. Notomi, J.-C. Picot, J.-F. Pradeau, M. Rashed, K. Sayre, R.K. Sprague, and J.G.C. Strachan.