（Ἀναξαγόρας). A Greek philosopher, of Clazomenae in Asia Minor, born about B.C. 500. Sprung from a noble family, but wishing to devote himself entirely to science, he gave up his property to his kinsmen, and removed to Athens, where he lived in intimacy with the most distinguished men-above all with Pericles. Shortly before the outbreak of the Peloponnesian War he was charged by the political opponents of Pericles with impiety, i.e. with denying the gods recognized by the State; and, though acquitted through his friend's influence, he felt compelled to emigrate to Lampsacus, where he died soon after, aged seventy-two. He not only had the honour of giving philosophy a home at Athens, where it went on flourishing for quite a thousand years, but he was the first philosopher who, by the side of the material principle, introduced a spiritual, which gives the other life and form. He laid down his doctrine in a work "On Nature" in the Ionic dialect, of which only fragments are preserved. Like Parmenides, he denied the existence of birth or death; the two processes were rather to be described as a mingling and unmingling. The ultimate elements of combination are indivisible, imperishable primordia of infinite number, and differing in shape, colour, and taste, called by himself "seeds of things," and by later writers (from an expression of Aristotle) ὁμοιομέρεια, i. e. particles of like kind with each other and with the whole that is made up of them. At first these lay mingled without order; but the divine spirit-νοῦς, pure, passionless reason-set the unarranged matter into motion, and thereby created out of chaos an orderly world. This movement, proceeding from the centre, works on forever, penetrating farther and farther the infinite mass. But the application of the spiritual principle was rather indicated than fully carried out by Anaxagoras: he himself commonly explains phenomena by physical causes, and only when he cannot find these, falls back on the action of divine reason. The fragments of his most important work were edited by Schaubach (1827), and by Schorn (1829). See also Beckel, Anaxagorae Doctrina de Rebus Animatis (Münster, 1868), and Ueberweg, Hist. of Philosophy, vol. i. pp. 63-67 (Eng. trans., N. Y. 1872). For criticism of Anaxagoras by Lucretius, see the De Rerum Natura, i. 830-920.
Anaxagoras (Greek: Ἀναξαγόρας, Anaxagoras, "lord of the assembly"; c. 500 BC – 428 BC) was a Pre-Socratic Greek philosopher. Born in Clazomenae in Asia Minor, Anaxagoras was the first philosopher to bring philosophy from Ionia to Athens. He attempted to give a scientific account of eclipses, meteors, rainbows, and the sun, which he described as a fiery mass larger than the Peloponnese. He was accused of contravening the established religion and was forced to flee to Lampsacus.
Anaxagoras is famous for introducing the cosmological concept of Nous (mind), as an ordering force. He regarded material substance as an infinite multitude of imperishable primary elements, referring all generation and disappearance to mixture and separation respectively.
Anaxagoras appears to have had some amount of property and prospects of political influence in his native town of Clazomenae in Asia Minor. However, he supposedly surrendered both of these out of a fear that they would hinder his search for knowledge. Valerius Maximus preserves a different tradition: Anaxagoras, coming home from a long voyage, found his property in ruin, and said: "If this had not perished, I would have." "This is a sentence - says the Roman - denoting the most perfect wisdom". Although a Greek, he may have been a soldier of the Persian army when Clazomenae was suppressed during the Ionian Revolt.
In early manhood (c. 464–461 BC) he went to Athens, which was rapidly becoming the centre of Greek culture. There he is said to have remained for thirty years. Pericles learned to love and admire him, and the poet Euripides derived from him an enthusiasm for science and humanity.
Anaxagoras brought philosophy and the spirit of scientific inquiry from Ionia to Athens. His observations of the celestial bodies and the fall of meteorites led him to form new theories of the universal order. He attempted to give a scientific account of eclipses, meteors, rainbows, and the sun, which he described as a mass of blazing metal, larger than the Peloponnese. He was the first to explain that the moon shines due to reflected light from the sun. He also said that the moon had mountains and he believed that it was inhabited. The heavenly bodies, he asserted, were masses of stone torn from the earth and ignited by rapid rotation. He explained that though both sun and the stars were fiery stones, we do not feel the heat of the stars because of their enormous distance from earth. He thought that the earth is flat and floats supported by 'strong' air under it and disturbances in this air sometimes causes earthquakes.  However, these theories brought him into collision with the popular faith; Anaxagoras' views on such things as heavenly bodies were considered "dangerous."
At about 450 B.C., Anaxagoras was arrested by Pericles' political opponents on a charge of contravening the established religion (some say the charge was one of Medism). It took Pericles' power of persuasion to secure his release. Even so he was forced to retire from Athens to Lampsacus in Troad (c. 434–433 BC). He died there in around the year 428 BC. Citizens of Lampsacus erected an altar to Mind and Truth in his memory, and observed the anniversary of his death for many years.
Anaxagoras wrote a book of philosophy, but only fragments of the first part of this have survived, through preservation in work of Simplicius of Cilicia in the sixth century AD.
All things have existed from the beginning. But originally they existed in infinitesimally small fragments of themselves, endless in number and inextricably combined. All things existed in this mass, but in a confused and indistinguishable form. There were the seeds (spermata) or miniatures of wheat and flesh and gold in the primitive mixture; but these parts, of like nature with their wholes (the homoiomereiai of Aristotle), had to be eliminated from the complex mass before they could receive a definite name and character. Mind arranged the segregation of like from unlike; panta chremata en omou eita nous elthon auta diekosmese. This peculiar thing, called Mind (Nous), was no less illimitable than the chaotic mass, but, unlike the logos of Heraclitus, it stood pure and independent (mounos ef eoutou), a thing of finer texture, alike in all its manifestations and everywhere the same. This subtle agent, possessed of all knowledge and power, is especially seen ruling in all the forms of life.
Mind causes motion. It rotated the primitive mixture, starting in one corner or point, and gradually extended until it gave distinctness and reality to the aggregates of like parts, working something like a centrifuge, and eventually creating the known cosmos. But even after it had done its best, the original intermixture of things was not wholly overcome. No one thing in the world is ever abruptly separated, as by the blow of an axe, from the rest of things.
It is noteworthy that Aristotle accuses Anaxagoras of failing to differentiate between nous and psyche, while Socrates (Plato, Phaedo, 98 B) objects that his nous is merely a deus ex machina to which he refuses to attribute design and knowledge.
Anaxagoras proceeded to give some account of the stages in the process from original chaos to present arrangements. The division into cold mist and warm ether first broke the spell of confusion. With increasing cold, the former gave rise to water, earth and stones. The seeds of life which continued floating in the air were carried down with the rains and produced vegetation. Animals, including man, sprang from the warm and moist clay. If these things be so, then the evidence of the senses must be held in slight esteem. We seem to see things coming into being and passing from it; but reflection tells us that decease and growth only mean a new aggregation (synkrisis) and disruption (diakrisis). Thus Anaxagoras distrusted the senses, and gave the preference to the conclusions of reflection. Thus he maintained that there must be blackness as well as whiteness in snow; how otherwise could it be turned into dark water?
Anaxagoras marked a turning-point in the history of philosophy. With him speculation passes from the colonies of Greece to settle at Athens. By the theory of minute constituents of things, and his emphasis on mechanical processes in the formation of order, he paved the way for the atomic theory.