留基伯Leucippus

留基伯（米利都的）继承了已经开始与米利都相关联的科学哲学。我们对他的生平知之甚少，但据认为他在色雷斯海岸、靠近奈斯托斯河口处的阿布德拉创办了学派。今天该镇位于希腊，名为阿夫季拉。在留基伯可能生活在阿布德拉的时期，它是一个繁荣的城镇，在政治上曾是提洛同盟的成员。

哲学家普罗泰戈拉出生于阿布德拉，他与留基伯是同时代人，但普罗泰戈拉，即智者中的第一位，一生大部分时间在雅典度过，可能在留基伯到达阿布德拉之前就已离开那里。尽管现在似乎几乎没有疑问留基伯存在过，但值得一提的是，公元前四世纪末的伊壁鸠鲁实际上认为留基伯从未存在过，因为关于他的所知甚少。然而，我们现在有足够的独立证据确信留基伯确实存在过。

亚里士多德称留基伯为一位哲学家，其观点与巴门尼德的观点颇为不同。亚里士多德多次提及他，并在若干场合引用他的著作。例如在De caelo中，亚里士多德写道：-

……在那些主张不可分量存在的人中，有些人，例如留基伯和德谟克利特，相信不可分的物体，另一些人，如色诺克拉底，则相信不可分的线。

遗憾的是，亚里士多德在提及留基伯时并不完全一致。有些引文表明原子论始于留基伯，另一些引文如上面那则则将留基伯和德谟克利特包括在内，而在少数地方，亚里士多德似乎暗示是德谟克利特独自发明了原子论。

当然，留基伯的思想似乎深受芝诺和巴门尼德的影响，但后来关于他是芝诺学生的说法似乎不太可能有什么真实性。更可能的是，后来的作者意识到留基伯遵循了芝诺的思想，而“学生”是在这个意义上使用的。

人们认为德谟克利特是留基伯的学生，这里的“学生”确实取其标准含义。他们二人被视为原子论的共同创始人。留基伯指出原子是[7]：-

……不可感知的、仅在形状和位置上有所不同的单个粒子。

这些粒子的混合产生了我们所经验到的世界。一些早期作者不相信留基伯的存在，其原因似乎在于他的观点与德谟克利特的观点完全交织在一起。很快，整个学说就被归到了两人中更为著名的德谟克利特名下。德谟克利特作为留基伯的学生，很可能发展了他老师的思想，但要分清两人对这一重要学说各自的贡献，则完全超出了我们的能力。

两部几乎可以肯定由留基伯写成的著作是The Great World System和On the Mind。其中第一部被泰奥弗拉斯托斯归功于留基伯。泰奥弗拉斯托斯（约公元前372年—公元前287年）是亚里士多德的学生，曾在雅典师从亚里士多德。泰奥弗拉斯托斯在公元前323年亚里士多德之后成为雅典吕克昂的负责人。他有能力区分留基伯的著作与德谟克利特的著作，我们将描述他对此事的看法。

Theophrastus声称，原子论的基本思想已存在于留基伯的哲学中，根据[1]：-

物质和虚空都真实存在。物质的构成要素是数目无限且永远运动着的元素，其形状有无限多的变化，在构成上完全坚实。

根据第欧根尼·拉尔修，留基伯在The Great World System中提出的宇宙论，是通过原子的偶然碰撞而聚集形成世界的一种创生。随后发生分化，较小的原子被抛入无限的空间，而其余原子则形成一个球形结构，较大的原子位于中心，较小的原子离中心更远。

从论著On the Mind中，我们得到了留基伯原话的唯一传世引文。在这部著作中，他写道（例如见[8]）：-

没有什么是徒劳发生的，一切皆出于理性与必然。

留基伯也为穷竭法做出了贡献。

Leucippus of Miletus carried on the scientific philosophy which had begun to become associated with Miletus. We know little of his life but it is thought that he founder the School at Abdera on the coast of Thrace near the mouth of the Nestos River. Today the town is in Greece and is called Avdhira. At the time that Leucippus would have lived in Abdera it was a prosperous town which politically was a member of the Delian League.

The philosopher Protagoras was born in Abdera and he was a contemporary of Leucippus but Protagoras, the first of the Sophists, spent most of his life in Athens and may have left Abdera before Leucippus arrived there. Although now there seems little doubt that Leucippus existed, it is worth remarking that Epicurus, at the end of the fourth century BC, actually believed that Leucippus had never existed since so little was known of him. However we now know enough in the way of independent evidence to be sure that Leucippus did exist.

Aristotle refers to Leucippus as a philosopher with rather different views to those of Parmenides. Aristotle refers to him several times and quotes from his works on a number of occasions. For example in De caelo Aristotle writes:-

... of those who have maintained the existence of indivisibles, some, as for example Leucippus and Democritus, believe in indivisible bodies, others, like Xenocrates, in indivisible lines.

Unfortunately Aristotle is not entirely consistent in his references to Leucippus. Some quotes suggest that atomism began with Leucippus, other quotes such as the one above bracket Leucippus and Democritus, while in a few places Aristotle seems to imply that Democritus alone invented atomism.

Certainly it seems that Leucippus was much influenced in his thinking by Zeno of Elea and by Parmenides, but it seems relatively unlikely that there is any truth in the later claim that he was a pupil of Zeno of Elea. More likely here is that later writers realised that Leucippus followed Zeno's ideas and 'pupil' was intended in this sense.

It is thought that Democritus was a pupil of Leucippus, where this time 'pupil' really does have its standard meaning. Together they are considered as the joint founders of atomic theory. Leucippus stated that atoms are [7]:-

... imperceptible, individual particles that differ only in shape and position.

The mixing of these particles gives rise to the world we experience. The reason that some early writers did not believe in the existence of Leucippus seems to be because his views and those of Democritus became completely entwined. Quite soon the whole became attributed to Democritus who was the more famous of the pair. It seems likely that Democritus as a pupil of Leucippus, developed the ideas of his teacher but it is quite beyond us to disentangle the contributions of each to this important doctrine.

Two works, almost certainly written by Leucippus, are The Great World System and On the Mind. The first of these is attributed to Leucippus by Theophrastus. Theophrastus (about 372 BC - 287 BC) was a pupil of Aristotle who had studied at Athens under Aristotle. Theophrastus became head of the Lyceum in Athens after Aristotle in 323 BC. He was in a position to be able to distinguish the works of Leucippus from those of Democritus and we shall describe his views on this matter.

Theophrastus claimed that the basic ideas of atomism were present in the philosophy of Leucippus according to which [1]:-

Both matter and void have real existence. The constituents of matter are elements infinite in number and always in motion, with an infinite variety of shapes, completely solid in composition.

According to Diogenes Laertius, the cosmology put forward by Leucippus in The Great World System is a creation of worlds by agglomerations of atoms by chance collisions. There is then differentiation with the smaller atoms being sent off into the infinity of space while the rest form into a spherical structure with the larger atoms at the centre and the smaller atoms further away from the centre.

From the treatise On the Mind we have the only quotation of the words of Leucippus which have survived. In this work he writes (see for example [8]):-

Nothing happens in vain, but everything from reason and of necessity.

Leucippus also contributed to the method of exhaustion.