a celebrated philosopher of antiquity, was a native of Abdera—an Ionian colony in Thrace. The date of his birth is not accurately known. By some authorities it is referred to the first year of the 80th Olympiad, i.e. 460 B.C.; by others to the year 470 B.C.; while Diodorus Siculus, perhaps the most reliable authority on this question, assigns it to B.C. 494. His father, whose name was Hegesistratus (though he is sometimes called Athenocritus and Damassipus), was an Abderitan of so great wealth, that when Xerxes passed through Abdera on his way back from Greece after Salamis, he entertained him and his suite with great magnificence. In return for this hospitality, the Persian monarch is said to have sent to Hegesistratus men skilled in all the learning of Persia and Chaldea, to teach the young Democritus the sciences then cultivated in the East. The immense wealth which he inherited from his father he spent in travel, visiting India, Chaldea, Persia, and Ethiopia. From these countries he is believed to have passed into Egypt, where he spent several years in studying the physical sciences which Pythagoras had learned there before him. It is not improbable that from Egypt he passed into Magna Graecia, where he found the minds of the people divided between the rival schools of Pythagoras and Zeno of Elea. From Italy he is said to have crossed over to Greece, attracted by the celebrity of Athens, where Socrates and Anaxagoras were then teaching, and to have attended the lectures of these philosophers incognito. A tradition also is current that he had a personal quarrel with Anaxagoras; but this is sufficiently refuted by certain passages in his own works, in which that philosopher is mentioned in terms of the highest praise. After wandering over nearly the whole of the then known world, he returned to his native Abdera so poor, despite his once large inheritance, that he was obliged to ask an asylum from his brother, by name Damassus. The history of his old age is even more obscure and contradictory than that of his youth. According to one tradition, he is said to have fallen into a state of imbecility, which so excited the sympathy of his countrymen, that they sent for the celebrated physician Hippocrates from Cos, and consigned the unfortunate philosopher to his care. According to other accounts, however, he is said to have prosecuted his studies without interruption almost till his death. The date of Democritus's death, like that of his birth, is very uncertain. By some he is said to have attained the great age of 109; by others, that of 104. Diodorus Siculus, whose version is probably the most reliable, states that at the time of his death Democritus had completed his 90th year. The memory of Democritus was held in high esteem by his countrymen, who, on his return home in poverty, are said to have presented him with large sums of money, and to have erected bronze statues to his honour in various parts of the town. His knowledge of natural science, in particular, is said to have proved on various occasions beneficial to the Abderitans, who honoured him on that account even more than on account of his philosophy. From the intensity of his application he is said to have injured his eye-sight so much that he ultimately became blind. On this story is founded the tradition of a later age, according to which he put out his eyes in order that his attention might not be distracted by the contemplation of a multiplicity of objects. His cheerfulness and humour he retained to the last; and, from his habit of viewing things on the bright side, and his extremely happy temperament, he earned for himself the title of the Laughing Philosopher. Heraclitus of Ephesus, who had regarded the world from the opposite point of view, had before this been familiarly known as the Weeping Philosopher.

According to Diogenes Laertius, Democritus was the author of seventy-two works. They are said to have comprised treatises on almost every subject of human inquiry. Of these, nothing has descended to our days except some titles and a few fragments. Some of these treatises are praised by Cicero as remarkable for the clearness and poetical beauty of the style, which, in his opinion, rivalled that of Plato. The fundamental ideas of Democritus's cosmological philosophy were borrowed from Leucippus, and were in direct opposition to those of the Eleatic school. These were, 1st, that a vacuum exists as well as its opposite, and that non-existence is no less true than existence; 2dly, that the divisibility of being, an inevitable consequence of the existence of a void, has necessarily limits. Here, at the very outset, may be discerned the materialistic character of this system; for the property which is here ascribed to being in general only belongs to matter, which alone can be limited and divided by space. Democritus endeavoured to prove the existence of a vacuum from motion, and from certain experiments originally devised by Leucippus. In his ethical philosophy Democritus maintained that peace of mind was the object to the attainment of which all our efforts should be directed. From notices and fragments of his works which have come down to us, it may be inferred that his ethical system contained much practical wisdom; and his ideas on Virtue and the Good are marked by a very high standard of moral aspiration.

The best collection of the fragments of Democritus is that by F. G. A. Mullach, 8vo, Berlin, 1843. His doctrines have given rise to much historical inquiry in modern times. They are fully discussed in the following works:—Magneni Democritus reviviscens, seu Vita et Philosophia Democriti, Pavia 1646, and Leyden 1648; Genderi Democriti Abderici, philosophus accuratissimus, ad superis vindicatus, Altona, 1765; Joachim, Prodr. de Democrito Philosocho, Leipzig, 1729; Plutarch, De Facultatibus Democriti Abderici, Tubingen, 1767; Illius, De Philosophia Epicuri Democritica, et Stoicoplatonica, Geneva, 1669; Gurltzi, Dissert. de Democriti Philosophia Real, 1703; Schwartz, Dissert. de Democriti Theologia, Coburg, 1718; Laskemann, Disput. Democriti Ethicorum Sectae Antitribus, Göttingen, 1718; Ritter, art. Democritus in Erck and Gruber's Dictionary, Leipzig, 1833; Benjamin Lafaist, Dissert. sur la Philosophie Atomistique, Paris, 1833; Ritter, History of Philosophy, vol. i. p. 559; Brandis, Klein. Mus., vol. iii. p. 133, &c.; and Papencordt, Atomistica Democriti.