an eminent philosopher of antiquity, was born at Clazomenae (now Kelissman), in the first year of the 70th Olympiad, or 500 B.C. (Apollodorus). His family was rich and noble, but he early sacrificed the prospects of worldly ambition to his passion for philosophy. Leaving his patrimony to be cultivated and enjoyed by his relations, he gave himself up to the contemplation of nature, which he regarded as the true object of man's existence. "To philosophy," he afterwards said, "I owe my worldly ruin, and my soul's prosperity." Some writers call him the pupil of Anaximenes; but this statement, if taken literally, is irreconcilable with chronology. According to others, he enjoyed the instructions of his countryman Hermotimus, who, according to Aristotle, was the first to proclaim the doctrine of a supreme regulative intelligence. At the age of 20, or according to others, of more than 40, he went to Athens, at that time entering on the most brilliant period of its history, and there continued for 30 years. His philosophical teachings soon drew around him the best intellects of Athens, and he numbered among his pupils Pericles, Euripides, Archelaus, and probably also Socrates. Without interfering in the public affairs of the state, he contented himself with forming the minds of its rising youth in the principles of wisdom. But neither the elevation and disinterestedness of his character, nor the powerful friendship of Pericles, could ward off the shafts of persecution. The philosopher was accused, like Socrates in the next generation, of impiety (ἀδελφεος) and enmity to religion, in introducing new and dangerous opinions concerning the gods. He was charged, among other things, with teaching that the moon was but a mass of matter like the earth, and the sun (the bright Apollo) a fiery mass of inanimate substance. The philosopher was tried and condemned to die; but the eloquence of Pericles procured the commutation of the sentence into a fine and banishment. Anaxagoras retired to Lampascus, where he continued to teach philosophy till his death in the 73rd year of his age, B.C. 428. "It is not I," said he in his exile, "who have lost the Athenians, but the Athenians who have lost me." The day of his death was for several centuries commemorated by a yearly holiday, called the Anaxagoria, in all the schools of Lampascus.

Opinions the most contradictory have been attributed to this philosopher. From the fragments that survive of his writings, and the statements of others regarding his opinions, it is impossible to obtain a systematic view of his doctrines. Diogenes Laertius, in his Life of Anaxagoras, has collected, with little care and judgment, details which were scattered through various writings. It appears that, in the midst of some extravagant conceptions, Anaxagoras held opinions which indicate a considerable acquaintance with the laws of nature. His idea of the heavens seems to have been that they were a solid vault, originally composed of stones elevated from the earth by the violent motion of the ambient ether, inflamed by its heat, and by the circular motion of the heavens fixed in their respective places. He considered the sun to be a fiery mass of stone larger than the Peloponnesus; and Xenophon introduces Socrates as refuting that doctrine, and delivering an unfavourable opinion concerning his other writings. The moon he believed to be inhabited, and to have its light reflected from the sun. Hence we find his disciple, Euripides, calling the moon not the sister, but the daughter, of the sun. From his perceiving that the rainbow is the effect of the reflection of the solar rays from a dark cloud, and that wind is produced by the rarefaction, and sound by the percussion of the air, he seems to have paid considerable attention to the phenomena of nature.

Our information is more correct concerning his opinions of the principles of nature and the origin of things. He imagined that in nature there are as many kinds of principles as there are species of compound bodies; and that the peculiar form of the primary particles of which any body is composed is the same with the quality of the compound body itself. For instance, he supposed that a piece of gold is composed of small particles which are themselves gold, and a bone of a great number of small bones: thus, according to Anaxagoras, bodies of every kind are generated from similar particles. The universe, according to him, consisted in the beginning of an infinite variety of these elementary principles (ἀρχαικόν), which were afterwards mixed and arranged by the moving force of intelligence (νοῦς). "He was the first," says Diogenes Laertius, "who superadded mind to matter, opening his work in this pleasing and sublime language:—All things were confused; then came mind and disposed them..." in order." Aristotle, in like manner, says, that he taught that intelligence was "the cause of the world, and of all order; and that while all things else are compounded, this alone is pure and unmixed." Reason (λόγος) he held to be the regulative principle of the mind, as the nous is of the universe. The senses inform us regarding external phenomena; but this information, he held, required the correction of reason. The fragments of Anaxagoras have been collected by Schaubach, Leipzig, 1827, and again in a better edition by Schorn, Bonn, 1829.