Biography:Leucippus

Short description: 5th-century BCE Greek philosopher

Leucippus
Leucippus by Luca Giordano (1652)
Born	5th century BCE
Era	Pre-Socratic philosophy
School	Atomism
Notable students	Democritus
Language	Ancient Greek
Main interests	Metaphysics, cosmology

Leucippus (/luːˈsɪpəs/; Greek: Λεύκιππος, Leúkippos; Template:Fl) was a pre-Socratic Greek philosopher. He is traditionally credited as the founder of atomism, which he developed with his student Democritus. Leucippus divided the world into two entities: atoms, indivisible particles that make up all things, and the void, the nothingness that exists between the atoms. He developed his philosophy as a response to the Eleatics, who believed that all things are one and the void does not exist. Leucippus's ideas were influential in ancient and Renaissance philosophy. His philosophy was a precursor to modern atomic theory, but the two only superficially resemble one another.

Leucippus's atoms come in infinitely many forms and exist in constant motion. This creates a deterministic world in which everything is caused by the collisions of atoms. Leucippus described the beginning of the cosmos as a vortex of atoms that formed the Earth, the Sun, the stars, and other celestial bodies. His model of the Earth was of a flat tilted disc, and night was caused by the Sun moving behind the lifted end of the Earth. As Leucippus considered atoms and the void to be infinite, he presumed that other worlds must exist as cosmoses are formed elsewhere. Leucippus and Democritus described the soul as an arrangement of spherical atoms, which are cycled through the body through respiration and create thought and sensory input.

The only records of Leucippus come from other ancient philosophers, particularly Aristotle and Theophrastus, and little is known of his life. Most scholars agree that Leucippus existed, but some have doubted his existence and instead attributed his ideas purely to Democritus. Two works are attributed to Leucippus, but all of his writing has been lost with the exception of one sentence. Modern philosophy rarely attempts to distinguish the ideas of Leucippus and Democritus.

Life

Almost nothing is known about the life of Leucippus. He was born in the first half of the 5th century BCE, but the exact dates are unknown. He presumably developed the philosophy of atomism during the 430s BCE. Most historical sources describe Leucippus as a student of Zeno of Elea, though Aristotle's writings on Leucippus do not support this. Melissus of Samos, Parmenides, and Pythagoras have all been suggested by ancient records as possible instructors of Leucippus. No students of Leucippus have been confirmed other than Democritus. Epicurus has been been described as a student of Leucippus, but Epicurus has also been recorded denying the existence of Leucippus.

Miletus, Elea, and Abdera have all been suggested as places where Leucippus lived, but these are most likely described as his home city because of their associations with other philosophers: Miletus was associated with the Ionian School that influenced Leucippus, Elea was associated with the Eleatic philosophers whom Leucippus challenged, and Abdera was the home of his student Democritus. One proposal is that he was born in Miletus before studying under Zeno in Elea and then settling in Abdera. There is no evidence from Leucippus's own lifetime about where he lived.

Philosophy

Atoms

Leucippus is credited with developing the philosophical school of atomism. He proposed that all things are made up of microscopic, indivisible particles that interact and combine to produce all the things of the world. The atoms postulated by Leucippus always hold the same shape and size, but they constantly change their position and their arrangements with one another, and they come in infinitely many shapes and sizes because there is no reason why they should not. According to Aristotle, he argued there must be indivisible points in a body, because bodies made entirely of divisible points would not be tangible. Leucippus developed atomism along with his student, Democritus; while Leucippus is credited with the philosophy's creation, Democritus is understood to have applied it to natural phenomena on a larger scale.

Two works are attributed to Leucippus: The Great World System and On Mind. The former may have originally been tilted The World System and then later renamed to avoid confusion with Democritus's The Little World System. Leucippus's The Great World System has sometimes been attributed to Democritus, which may have been an effect of Democritus including it among his corpus as the foundation of his work. Only one extant fragment is attributed to Leucippus, taken from On Mind: "Nothing happens at random, but everything from reason and by necessity". Leucippus believed that all things must happen deterministically, as the positions and motions of the atoms guarantee that they will collide in a certain way, invoking the principle of causality. This was reminiscent of Anaximander's argument that movement is created by differences, and it was later codified by the 17th century philosopher Gottfried Wilhelm Leibniz with the principle of sufficient reason. Leucippus rejected the idea that there was an intelligent force governing the universe.

Eleatics and the void

Leucippus's atomism was a direct response to Eleatic philosophy. The Eleatics believed that nothingness, or the void, cannot exist in its own right. They concluded that if there is no void, then there is no motion and all things must be one. Leucippus agreed with their logic, but he asserted that the void did exist, and he was therefore able to accept the existence of motion and plurality. Like the Eleatics, Leucippus believed that everything exists in an eternal state and nothing can come into or out of existence, applying this to both atoms and the void. Aristotle described Leucippus as saying that atoms are not an addition to the void, but that atoms and the void are two opposites that exist beside one another. Simplicius of Cilicia contradicted Aristotle's account, attributing this idea to Democritus. According to the Roman philosopher Lactantius, Leucippus compared atoms to the particles of floating dust that are visible in sunlight.

Leucippus's atomism applied the ontology of Eleatic philosophy to an empirical understanding of the world being an entirely physical phenomenon. By moving away from the abstract points and units of geometry, he formed a possible solution to the paradoxes of motion created by Zeno of Elea. Leucippus also contested the Eleatic argument against divisibility: that any divider between two objects can also be divided. He argued that the void is a divider that does not have being and therefore cannot be divided. Though Leucippus described atoms as being able to touch one another, Aristotle understood this to mean atoms being near one another, as Leucippus maintained that the void must exist between all atoms. The 20th century philosopher Ernst Cassirer described Leucippus's philosophy as the third and final stage in the shifting understanding of foundation from the Eleatic analytic logic to the atomist causal logic, following Empedocles and Anaxagoras.

Soul and perception

Leucippus and Democritus proposed that heat, fire, and the soul are made of spherical atoms, as these are most able to move past one another and cause the others to move. They believed in a material soul that drives motion in living things, and they described respiration as the process of expelling soul atoms and absorbing new ones. Death then coincides with the last breath, as soul atoms are no longer being replenished. Sleep is a similar state in which a reduced number of soul atoms are in the body.

Along with Democritus, Leucippus was the first philosopher to describe a theory of thought and perception. He described sensory input as transfers from external atoms through physical contact to the atoms of the soul. Leucippus described sight as a film of atoms emitted from an object, maintaining the shapes of its atoms and creating a reflection of the object in the viewer's eye. His description of vision was inspired by Empedocles, who formed a similar concept of objects emitting films of themselves. He posited that concepts such as color and texture are created by different arrangements of atoms, and that abstract concepts such as justice and wisdom are produced through the arrangement of soul atoms. Leucippus has variously been described as saying that reasoned knowledge is impossible to obtain and that sensory input provides objective truth.

Cosmology

Leucippus asserted the existence an infinite number of atoms and a void that extends infinitely. The Earth and the cosmos, including the Sun, the Moon, and the stars, exist together alongside the much broader void. Leucippus's account of the cosmos began with atoms moving around the void as a vortex. The atoms of the vortex shifted among one another until they were sorted "like to like". The smallest atoms were pushed to the edge of the vortex as celestial bodies, and the remaining atoms created a membrane from which the Earth was formed. The ancient Greek biographer Aetius interpreted this to mean that the smaller atoms formed a membrane around the larger ones, while the Roman biographer Diogenes Laertius interpreted this to mean that the larger atoms formed a membrane and the smaller ones were excluded. Leucippus is the first known philosopher to propose the existence of other worlds; he believed in an infinite void and infinite atoms, so he presumed that there must be other groups of atoms creating vortexes and cosmoses elsewhere.

In his positioning of heavenly bodies, Leucippus said that the Sun was the farthest entity from the Earth. The stars ignited as they were spinning the fastest, and they in turn ignited the Sun. Leucippus adopted the idea of the Ionian philosophers that the Earth was flat and rested atop air. Adopting the ideas of Anaxagoras, he described the Earth as a disc tiltedon its horizontal axis, so that night is caused by the Sun moving behind the raised northern end of the Earth.

While the curved trajectories of the cosmos necessitated some philosophers to postulate a non-earthly substance that composes the celestial bodies, Leucippus's vortex model provided an explanation for both heavenly and earthly movement. It is unclear whether Leucippus considered vortexes to arise by chance or by necessity. Leucippus gave no explanation for how motion began, for which he was criticized by Aristotle. The generation and destruction of atomic structures described by Leucippus are a form of motion under this system.

Legacy

A line engraving of Leucippus by S. Beyssent

Ancient Greece

Modern understanding of Leucippus's role in the development of atomism comes from the writings of the ancient Greek philosophers Aristotle and Theophrastus. Aristotle's record of Leucippus and Democritus's philosophy is the oldest surviving source on the subject, thought he did not distinguish who developed which atomist ideas. Aetius also wrote a history of Leucippus, but it was well after Leucippus's own time and derivative of previous writings on the subject. Some later histories of philosophy omitted Leucippus entirely. Since ancient times, Leucippus has languished in obscurity compared to Democritus, and since the earliest records is has been common practice to consider the atomist ideas of Leucippus and Democritus collectively rather than attempting to distinguish them.

The atomist philosophy of Leucippus and Democritus influenced Greek philosophy for centuries, particularly in the work of Aristotle and Epicurus. Aristotle challenged atomism because he deemed it insufficient to explain why stone falls but fire rises. It is unclear whether Leucippus's contemporary Diogenes of Apollonia responded to Leucippus or if Leucippus responded to Diogenes, but Diogenes's interpretation of the void may have been inspired by Leucippus. Plato explored cosmological ideas similar to those of Leucippus in the dialogue Timaeus.

Modern era

Ancient atomism was revived in the 16th and 17th centuries, when Pierre Gassendi was its most prominent advocate. It was influential in the development of early atomic theories in the 18th and 19th centuries, and Leucippus's theory of change regarding the movement of atoms was generally accepted in physics until the early 20th century.

The 20th century philosopher Adolf Dyroff (de) developed a set of distinctions between Leucippus and Democritus: he proposed that Leucippus was responsible for the atomist response to the Eleatics while Democritus responded to the Sophists and that Leucippus was a cosmologist while Democritus was a polymath. The 20th century classicist Cyril Bailey proposed another system to differentiate the two philosophers, attributing atomism and belief in the void to Leucippus while attributing The Great Cosmology to Democritus as an application of Leucippus's philosophy. Unlike Democritus, Leucippus is only known to have studied cosmology and physics, and he is not known to have produced any writings on ethics or epistemology.

Modern philosophy generally takes more interest in Leucippus's atomism than his cosmology. The ideas originating from Leucippus are a precedent for modern atomic theory, although the two theories only resemble each other superficially. Leucippus's philosophy was conjecture based on a priori evidence, while modern atomic theory is supported by empirical evidence found through the scientific method. The main practical difference between Leucippus's atomism and modern atomic theory is introduction of non-tangible phenomena such as mass–energy equivalence and fundamental forces. Instead of the purely material atoms of Leucippus, modern atomic theory shows that fundamental forces combine subatomic particles into atoms and link atoms together into molecules. The 20th century physicist Werner Heisenberg argued that Plato's theory of forms was closer to reality than Leucippus's conception of atoms, saying that modern atoms are more like the intangible Platonic forms than the discrete material units of Leucippus.

Historicity

According to Diogenes Laertius, Epicurus alleged that Leucippus never existed—an allegation that triggered extensive philosophical debate. Most modern philosophers agree that Leucippus existed, but there is disagreement on whether his work can be meaningfully distinguished from that of Democritus. No significant work on the historicity of Leucippus has been produced since the early 20th century.

Scholars who maintain that Leucippus existed argue that he only taught orally or that any written works he produced were never meant for publication. The 20th century classicist John Burnet proposed an alternate reading of Epicurus, in which he may have been saying that Leucippus was not worth discussing as a philosopher. Supporting this argument is that Epicurus considered ethics to be foundational to philosophy, and Leucippus had no teachings on that subject. Among scholars who argue against Leucippus's existence, alternate ideas have been proposed: Leucippus may have been a pseudonym of Democritus, or he may have been a character in a dialogue. Modern scholars who have rejected the existence of Leucippus include Erwin Rohde, Paul Natorp, Paul Tannery, P. Bokownew, Ernst Howald (de), Herman De Ley ({{{2}}}), Adolf Brieger (de), and Wilhelm Nestle.

The existence of Leucippus was an issue in 19th century German philosophy, where it spawned a debate between Rohde, Natorp, and Hermann Alexander Diels. Rhode believed that even in the time of Epicurus there was no evidence of Leucippus's existence, and there was therefore no purpose in attributing the atomism of Democritus to an unknown figure such as Leucippus, rejecting Theophrastus's account. Natorp likewise rejected that Diogenes of Apollonia was preceded by Leucippus. Diels affirmed the account of Theophrastus and produced writings criticizing Rhode and Natorp. Such was the problem's enormity that it was given its own name in German: die Leukipp-frage.

See also

• Kanada – An ancient Indian philosopher who also developed an early atomist philosophy

References

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