Probably as a consequence of the negative judgement which often weighed against them – yet not unlike the case for many other ancient writers – almost no complete texts by the sophists survive: we must rely on quotes and testimonies. Although recently discovered papyri have broadened our knowledge, to this day the essential edition of the works of the sophists – and Presocratic philosophers more generally – is Hermann Diels's Die Fragmente der Vorsokratiker, later revised and corrected by Walter Kranz (Diels and Kranz 1951–2, henceforth D.-K.). This collection is in three volumes: the first two contain all the sources, arranged in ninety chapters (each chapter usually corresponding to an author), while the third volume features a word index and a selective index of names and passages. The section on the sophists coincides with Chapters 79–90 of the second volume. For each author, the chapters are divided into ‘testimonies’ and ‘fragments’, which are respectively marked with the letters A and B (this subdivision is not adopted in all cases, but only when the number of passages allows it – this is not the case, for instance, with Xeniades, Lycophron, and the Dissoi logoi); in some cases we also find a third section, C, containing ‘imitations’. Thus 80B3 will stand for fragment 3 of Protagoras, while 87A6 will stand for testimony 6 on Antiphon, and so on (the same criteria generally apply to all other Presocratic philosophers as well).

Though yet unsurpassed, Die Vorsokratiker can now be fruitfully complemented with a new impressive collection of testimonies and fragments: André Laks and Glenn W. Most, Early Greek Philosophy, published in 2016 in the Loeb Classical Library (and in French by Fayard with the title Les débuts de la philosophie. Des premiers penseurs grecs à Socrate, henceforth L.-M.). The sophists are presented in the eighth and ninth volumes, sections 31–42. Each chapter normally comprises three sections, with each entry being identified by a number preceded by a letter: P indicates information on the life, character, and sayings of a given philosopher; D the doctrines; R the reception of their thought and writings. Unless not otherwise noted, all translations of the sophists are based on Laks and Most's translations. Other useful translations are Freeman 1948, Kent Sprague 1972, and Dillon and Gergel 2003. With regard to Plato and Aristotle, our two most important testimonies regarding the sophists, the translations are taken from Cooper 1997 and Barnes 1984, respectively. For all the other authors, the translations are from the Loeb Classical Texts (with minor changes).

This book, a revised and updated version of my previous book, I sofisti (Rome, 2010), would never have seen the light without the support and the competence of the editor of the New Surveys series, Phillip Horky. My warmest thanks are due to him, and also to Sergio Knipe for his help with the translation.