Leucipo

Leucippus (5th century bc)

The early Greek philosopher Leucippus was the founder of atomism. Virtually nothing is known of his life, and his very existence was disputed in antiquity, but his role as the originator of atomism is firmly attested by Aristotle and Theophrastus, although the evidence does not allow any distinction between his doctrines and those of his more celebrated successor Democritus. He wrote a comprehensive account of the universe, the Great World-System. The single surviving quotation from his work asserts universal determinism.

Leucippus was a shadowy figure even in antiquity. Virtually nothing is known of his life. His birthplace was disputed; some sources associated him with one or other of the two principal centres of early Greek philosophy, Elea and Miletus, others with Abdera, the birthplace of Democritus. The statement in a number of sources that he was a pupil of Zeno of Elea may be merely an inference from the Eleatic influence on the foundations of atomism (see Democritus §2). Of his dates, all that can be said is that he lived during the fifth century bc: he was almost certainly older than Democritus, who is described by Aristotle and Simplicius as his ‘associate’ (hetairos), implying that Democritus was his pupil (as is also attested by Diogenes Laertius). In the post-Aristotelian period he was overshadowed by Democritus to such an extent that atomism came generally to be regarded as the work of the latter, while Epicurus and his successor Hermarchus are reported to have denied that Leucippus ever existed. His historicity is, however, firmly attested by Aristotle, who is the primary source for atomism. No list of Leucippus’ works exists. The catalogue of works of Democritus produced by Thrasyllus in the first century ad contains two books entitled World-System (diakosmos), respectively, the Great World-System and the Small World-System, with a note that the school of Theophrastus attributed the former to Leucippus. It is probable that that attribution is correct, the attribution to Democritus being due to the overshadowing process mentioned above. The single quotation surviving from Leucippus is said by its source, Stobaeus, to come from a work On Mind; it is uncertain whether that title refers to a section of the Great World-System or to a separate work. The pseudo-Aristotelian treatise On Melissus, Xenophanes and Gorgias refers to ‘the so-called arguments of Leucippus’, presumably a reference to a work purporting to be by Leucippus.

Aristotle, followed by Simplicius, sometimes attributes the fundamentals of atomism to Leucippus (see, for example, Aristotle, On Generation and Corruption 325a23, b7). Elsewhere, however, and sometimes even in the same context (for example, On Generation and Corruption 325a1–2) Aristotle refers to Leucippus and Democritus jointly, and not infrequently to Democritus alone (as was the standard practice of later writers). That Leucippus was in some sense the pioneer is undoubted, but it is impossible to determine what elements of the theory of atomism are to be attributed to either, or to what extent their enterprise was collaborative. (For discussion of the principles of atomism, see Democritus (§2).) Of the two most detailed reports of the atomists’ account of the formation of worlds, one is attributed by Diogenes Laertius to Leucippus (IX 30–3), and is presumably a summary of the account in the Great World-System. It ascribes the formation of worlds to agglomerations of atoms which, formed by chance collisions, develop a rotation in which atoms of different sizes are sifted out, the smaller being extruded into the infinity of space, the larger forming a spherical structure which gradually differentiates itself into a cosmos as the larger atoms sink to the centre and the smaller are forced to the outside. The rotation of the cosmic aggregates was apparently unexplained, and was according to some sources attributed to chance. This raises the question whether Leucippus believed that some events, such as the cosmic rotation, are objectively random, or are merely ascribed to chance in the weaker sense that their cause is undiscoverable. The single quotation, ‘Nothing happens in vain, but everything from reason and of necessity’ (fr. 2, Stobaeus, I 4.4), suggests the latter. While it could in isolation be understood as asserting universal purposiveness in nature, the secondary sources, including Aristotle, are unanimous that the atomists denied all purposiveness in natural events. Hence the quotation is best understood as asserting universal determinism; ‘in vain’ is understood as ‘for no reason’, and ‘of necessity’ specifies the reason for which everything happens – namely, the irresistible force of causation. On that interpretation, the cosmic rotation must have had some determinate cause, but a cause undiscoverable to us.