In accordance with the purpose of the series Traditio Praesocratica, the present volume, the first in the series, contains the most complete collection ever assembled of the documentary evidence on Thales of Miletus. Approximately 600 texts, dating from the sixth century BCE to the fourteenth century CE, are presented in chronological order, both in the original language (Greek, Latin, Arabic and Persian) and in a facing English translation. The original-language texts are reprinted (with corrections) from Georg Wöhrle's edition (2009). Several texts discovered since the publication of the 2009 edition are included. The English translations were made by Richard McKirahan from the original texts. Differences between the German and the English translations are noted. An index of names and extensive glossaries and word indexes of the texts and translations are provided.