The men and their books

The writers of the ancient world were confident that Leucippus and Democritus were the founders of the atomic theory, but they were not at all careful in allocating the credit between the two of them. Attempts have been made by modern scholars to isolate the contribution of Leucippus – the earlier and less well-known of the two – but their arguments, if not demonstrably wrong, are too tenuous to rely on. Little attempt will be made in this book to distinguish their doctrines, at least with regard to the physical world; on the subject of human society and ethics, it appears that Democritus was very much the major contributor.

The early Atomists are associated with the remote country town of Abdera, on the northern Greek mainland close to the island of Thasos. Democritus lived and worked there; probably Leucippus did so too, although ancient biographers were uncertain whether to connect him with Abdera, Elea, or Miletus. Democritus had a long life – some say he lived to be a hundred. His precise dates are not known. He himself wrote in The Small World Order, according to Diogenes Laertius (IX.41), that he was forty years younger than Anaxagoras. Probably he was born about 460 b.c., and Leucippus was somewhat older. The atomic theory, then, must date from about the time of the Peloponnesian War, in the last decades of the fifth century; it is approximately contemporary with Socrates' philosophical activity, and with the birth of Plato.