Leucippus

This article is about the philosopher. For other uses, see Leucippus (disambiguation).

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; fl. 5th century BCE) was a pre-Socratic Greek philosopher. He is traditionally credited as the first philosopher to develop a theory of atomism. This is a distinction he shares with his student, Democritus, and which of them developed atomism is the subject of debate. Some philosophers argue that there was no historical Leucippus and that atomism was invented entirely by Democritus. Two books are attributed to Leucippus, but little else is known about his life or his teachings. Modern philosophy rarely attempts to distinguish the work of Leucippus and Democritus.

Philosophy

Atomism

Leucippus is described as the founder of atomism, the theory that all things are made up of atoms. These atoms are microscopic, indivisible objects that interact and combine to produce all the things of the world. They are described as constantly holding the same shape and size but always changing their position and their arrangements with one another in constant motion. Leucippus held that atoms can take on any shape, size, or position because there is no reason why they should not, and he described a state of constant generation and destruction.

Leucippus developed atomism along with his student, Democritus. Since ancient times, Leucippus has languished in obscurity compared to Democritus. While Leucippus is credited with the philosophy's creation, Democritus is understood to have applied it to natural phenomena on a larger scale. It is common practice in modern philosophy to consider the atomist ideas of Leucippus and Democritus collectively rather than attempting to distinguish them.

Two works are attributed to Leucippus: The Great World System and On Mind. Only one extant fragment is attributed to Leucippus, taken from On Mind: "Nothing happens at random, but everything from reason and by necessity". This means that all things have to happen deterministically because of the positions and motions of the atoms, invoking the principle of causality. This was reminiscent of Anaximander's argument that movement is created by differences, and it was later codified by Gottfried Wilhelm Leibniz with the principle of sufficient reason. Leucippus rejected the idea that there was an intelligent force governing the universe.

According to Aristotle, Leucippus argued there must be indivisible points in a body, because a body made entirely of divisible points would not be tangible, and that the entire universe would fall apart. 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 nothingness, or the void, must exist between all atoms. According to Lactantius, Leucippus compared atoms to the particles of floating dust that are visible in sunlight.

Along with Democritus, Leucippus was the first philosopher to describe a theory of thought and perception. He posited that more complex 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 specialized "soul atoms". Leucippus created a basic description of sensory input, saying that senses are transfers from external atoms through physical contact to the atoms of the soul. His description of vision was inspired by Empedocles, who said that objects emit films of themselves. Leucippus described these films as atoms in the same shape of the object, emitted in a way that create a reflection of the object in the viewer's eye. Democritus adopted a similar theory, saying that the image was created when the film came into contact with the air, creating an impression of the object. Leucippus has variously been described as saying that reasoned knowledge is impossible to obtain and that sensory input provides objective truth.

Relationship to the Eleatics

According to Aristotle, Leucippus developed atomism as a challenge to the philosophy of the Eleatics. The Eleatics believed that the void cannot exist. They also believed that everything can be infinitely divided. Aristotle tells that while Leucippus agreed with their concept of void, he contended that it did exist and that things cannot be divided forever. He believed that if there were no void, then all of reality would be a single indivisible, all-encompassing mass. To Leucippus, atoms were not an addition to void, but atoms and void were two equal opposites that existed beside one another, and both were subject to the Eleatic concept of existence as an eternal state.

Leucippus's atomism applied the ontology of Eleatic philosophy to an empirical understanding of the world being an entirely physical phenomenon. By accepting the existence of void, Leucippus was also able to accept the existence of motion, plurality, and divisibility—all concepts rejected by the Eleatics. This provided him a solution to the paradoxes of motion created by Zeno of Elea. It is possible that some Eleatic philosophers, such as Melissus, were responding to atomism instead of the reverse.

Cosmology

Leucippus asserted the existence of the void, or empty space. The void extends infinitely, populated with infinitely many atoms. The Earth and the cosmos, including the sun, the moon, and the stars, exist together within the much broader void. Under Leucippus's model, the cosmos was formed when atoms moved around the void as a vortex. The atoms of the vortex shifted among one another until they were sorted "like to like". The finest atoms were pushed to the edge of the vortex, and the remaining atoms formed a membrane from which the celestial bodies were constructed. The stars ignited as they were spinning the fastest, and they in turn ignited the sun. A similar concept of the cosmos was later explored by Plato in his Timaeus. Leucippus also described the existence of multiple cosmos being created and destroyed.

In his organization of the cosmos, Leucippus adopted the idea of Anaximenes that the Earth was flat and rested atop air, and that it revolved around the vortex that birthed the cosmos. In the positioning of heavenly bodies, he said that the sun was the farthest entity from the Earth, as opposed to Democritus, who argued that the stars were farther away. 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. He gave no explanation of how motion began, a deficiency for which he was repeatedly criticized by Aristotle.

Life

Almost nothing is known about the life of Leucippus. He is described as having been born in the first half of the 5th century BCE, but the exact dates are unknown. Miletus, Elea, and Abdera have all been suggested as places where he lived, but these are most likely described as his home city because of their associations with other philosophers. Miletus is 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. There is no evidence from Leucippus's own life about where he lived or whether he even existed. Leucippus presumably developed atomism during the 430s BCE. Unlike Democritus, Leucippus is only known to have studied cosmology and physics.

According to Diogenes Laertius, Leucippus was a student of Zeno of Elea. He was also a contemporary of Melissus of Samos; Melissus has been credited as Leucippus's instructor, but this is not widely accepted. In addition to Democritus, Epicurus has been described as a student of Leucippus, although Epicurus has also been recorded denying the existence of Leucippus.

Legacy

A line engraving of Leucippus by S. Beyssent

The oldest record of Leucippus and Democritus's ideas was written by Aristotle. He documented their philosophy, but he did not distinguish who developed which atomist ideas. The ideas of Leucippus and Democritus continued to influence Greek philosophy for centuries, including 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 Diogenes of Apollonia responded to Leucippus or if Leucippus responded to Diogenes; Leucippus may have inspired Diogenes' interpretation of the void.

Ancient atomism was revived during the 17th century, 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 ideas originating from Leucippus are a precedent for modern atomic theory, although the two theories only resemble each other superficially. Since the development of modern atomic theory, aspects that contradict Leucippus's atomism have been discovered, including modern chemistry, brownian motion, fundamental interactions, and mass–energy equivalence. The physicist Werner Heisenberg argued that Plato's theory of forms was closer to reality than Leucippus's conception of atoms.

Historicity

Epicurus is said to have alleged that Leucippus never existed—an allegation that triggered extensive philosophical debate. Modern philosophers disagree over the historicity of Leucippus, and among those who maintain his existence, there is disagreement whether his work can be meaningfully distinguished from that of Democritus. Scholars who maintain that Leucippus existed argue that he only taught orally or that any written works he produced were never meant for publication. 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.

The existence of Leucippus was a major issue in 19th century German philosophy, where it spawned a debate between Erwin Rohde, Paul Natorp, and Hermann Alexander Diels. Rohde and Natorp disputed the attribution of On Mind to Leucippus, and Rohde argued that Democritus should be credited with The Great Cosmology. Rohde also argued that there was no extant writing of Leucippus by the time of Epicurus. In response, Diels defended the attribution of On Mind to Leucippus.

Adolf Dyroff 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. 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.

See also

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

References

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