|Born||Early 5th century BCE
Abdera or Miletus
|Died||5th century BCE|
|School||Pre-Socratic philosophy: Atomism, Materialism|
Leucippus or Leukippos (Greek: Λεύκιππος, first half of 5th century BCE) was one of the earliest Greeks to develop the theory of atomism — the idea that everything is composed entirely of various imperishable, indivisible elements called atoms — which was elaborated in greater detail by his pupil and successor, Democritus.
According to this atomism, if you take a piece of wood and then cut it into two equal parts, then do it continuously, eventually you will find a part that you can't cut. This smallest possible part is the "atom". A possible earlier candidate for atomism is Mochus of Sidon, from the Trojan War era (13th or 12th century BCE).
Leucippus is a shadowy figure, as his dates are not recorded and he is often mentioned in conjunction with his more well-known pupil Democritus, who replaced indeterminism with determinism as the ontological cause of atomic movement. It is therefore difficult to determine which contributions come from Democritus and which come from Leucippus.
In his Corpus Democriteum, Thrasyllus of Alexandria, an astrologer and writer living under the emperor Tiberius (14-37 CE) compiled a list of writings traditionally attributed to Democritus to the exclusion of Leucippus.
Leucippus was an Ionian Greek (Ionia, now part of western Turkey), as was Anaxagoras. And he was a contemporary of Zeno of Elea and Empedocles (Magna Graecia, now part of southern Italy). He belonged to the same Ionian School of naturalistic philosophy as Thales, Anaximander, Anaximenes, and he was interested in reality and not idealism as the Italic Eleatics were. Later stories about the influence of Zeno have been questioned by modern studies, also because the ontological conception of being of the Eleatics is static, monistic and deterministic, while Leucippus' is dynamic, pluralistic and indeterministic.
Around 440 or 430 BCE Leucippus founded a school at Abdera, which his pupil, Democritus, was closely associated with. His fame was so completely overshadowed by that of Democritus, who systematized his views on atoms, that Epicurus doubted his very existence.
However, Aristotle and Theophrastus explicitly credit Leucippus with the invention of Atomism. Leucippus agreed with the Eleatic argument that true being does not admit of vacuum, and there can be no movement in the absence of vacuum. Leucippus contended that since movement exists, there has to be vacuum. However, he concludes that vacuum is identified with non-being, since it cannot really be. Leucippus differed from the Eleatics in not being encumbered by the conceptual intermingling of being and non-being. Plato made the necessary distinction between grades of being and types of negation.
The most famous among Leucippus' lost works was titled Megas Diakosmos (The Big World-System, or Great Cosmology, which was sometimes described as a work of Democritus like the Micros Diakosmos or Little World-System) and Peri Nou (On mind).
Fragments and doxographical reports about Leucippus were collected by Hermann Diels (1848–1922), firstly in Doxographi Graeci (Berlin, 1879, reprint Berlin: de Gruyter, 1929) and then in Die Fragmente der Vorsokratiker, Berlin, 1903, 6th ed., rev. by Walther Kranz (Berlin: Weidmann, 1952; the editions after the 6th are mainly reprints with little or no change.) One fragment of Leucippus which is probably accurate is the Great Cosmology fragment that says: "The cosmos, then, became like a spherical form in this way: the atoms being submitted to a casual and unpredictable movement, quickly and incessantly." (24, I, 1)
See also 
- The Cambridge Companion to Early Greek Philosophy, pg. xxiii. Note that Democritus was a resident of Abdera. Some said Leucippus from Elea, perhaps since he was unsuitably associated with the Eleatic philosophers.
- Diogenes Laërtius says "Leucippus was born at Elea, but some say at Abdera and others at Miletus," Diogenes Laërtius, ix. 30. Simplicius refers to him as "Leucippus of Elea or Miletus," Simplicius, Physica, 28, 4
- Jonathan Barnes, Early Greek Philosophy, 1987
- Leucippus, in The Presocratics, Philip Wheelwright ed., The Odyssey Press, 1966, pg. 177.
- Diogenes Laërtius x. 7
- The Cambridge Companion to Early Greek Philosophy, pg. xxiii
- Stobaeus, i. 4. 7c
- A. A. Long (ed.), The Cambridge Companion to Early Greek Philosophy (pgs. xxiii, 185)
- Diels-Kranz, Die Fragmente der Vorsokratiker [I] 67A
- Diogenes Laërtius, Lives and Opinions of Eminent Philosophers, IX.30-33
- Leucippus entry by Sylvia Berryman in the Stanford Encyclopedia of Philosophy
- Diogenes Laërtius, Life of Leucippus, translated by Robert Drew Hicks (1925).