Hermann Diels (1848-1922), professor of classics at Berlin, is chiefly remembered for this collection of quotations from, and reports about, Presocratic philosophers; his system of numbering was later adopted as the scholarly standard. This reissue reproduces the original, single-volume edition of 1903, though the book was revised and expanded three times during Diels’ lifetime, and again after his death, and new fragments continue to be discovered. Designed as a reference tool to underpin university classes on the beginnings of Greek philosophy, the book sought to enable students to engage with original evidence. Diels aimed to provide a complete corpus of fragments rather than an arbitrary selection. He intentionally reproduced the texts exactly rather than standardising the language, in order to provide a foundation for future research. While admitting he found the material obscure at times, Diels provided German translations to help make the content more accessible to his readers.