He is now known for a collection of quotations from and reports about Presocratic philosophers.[a] This work, entitled Die Fragmente der Vorsokratiker (The Fragments of the Pre-Socratics), is still widely used by scholars. It was first published in 1903, was later revised and expanded three times by Diels, and was finally revised in a 5th edition (1934–7) by Walther Kranz and again in a sixth edition (1952). It consists of three volumes that present, for each of the Presocratics, both quotations from their (now mostly lost) works transmitted by later writers, and secondary-source material known as testimonia.[b]
Based on Diels' enumeration of the fragments, the testimonia in the Diels collection are known as the "A-fragments", while the quotations from the Presocratics are known as the "B-fragments". Diels's method of labeling the fragments has become the standard way of referring to the works of the Presocratics.
An English translation or paraphrase of each of the B-fragments in Diels–Kranz may be found in Kathleen Freeman's Ancilla to the Pre-Socratic Philosophers (Oxford, 1948; Harvard U. Press, 1957), though it is based on the fifth edition of Diels–Kranz, whose numbering of fragments is somewhat different from later editions. (accessible via scribd)
