Anaxagoras (Αναξαγόρας) (c. 500 BC–428 BC), a Greek philosopher, was born probably about the year 500 BC (Apollodorus ap. Diog. Laert. ii. 7.).

At his native town of Clazomenae in Asia Minor, he had, it appears, some amount of property and prospects of political influence, both of which he surrendered, from a fear that they would hinder his search after knowledge. Nothing is known of his teachers; there is no reason for the theory that he studied under Hermotimus of Clazomenae, the ancient miracle-worker.

In early manhood (c. 464-462 BC) he went to Athens, which was rapidly becoming the headquarters 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. Some authorities assert that even Socrates was among his disciples. His influence was due partly to his astronomical and mathematical eminence, but still more to the ascetic dignity of his nature and his superiority to ordinary weaknesses—traits which legend has embalmed. It was he who brought philosophy and the spirit of scientific inquiry from Ionia to Athens. His observations of the celestial bodies led him to form new theories of the universal order, and brought him into collision with the popular faith. He attempted, not without success, to give a scientific account of eclipses, meteors, rainbows and the sun, which he described as a mass of blazing metal, larger than the Peloponnesus; the heavenly bodies were masses of stone torn from the earth and ignited by rapid rotation. The polytheism of the time could not tolerate such explanation, and the enemies of Pericles used the superstitions of their countrymen as a means of attacking him in the person of his friend.

Pericles and Anaxagoras, Belle Augustin-Louis

Anaxagoras was arrested on a charge of contravening the established dogmas of religion (some say the charge was one of Medism), and it required all the eloquence of Pericles to secure his release. Even so he was forced to retire from Athens to Lampsacus (434-433 BC), where he died about 428 BC, honoured and respected by the whole city.

It is difficult to present the cosmological theory of Anaxagoras in an intelligible scheme. All things have existed in a sort of way from the beginning. But originally they existed in infinitesimally small fragments of themselves, endless in number and inextricably combined throughout the universe. All things existed in this mass, but in a confused and indistinguishable form. There were the seeds (spermata) or miniatures of corn and flesh and gold in the primitive mixture; but these parts, of like nature with their wholes (the omoiomere of Aristotle), had to be eliminated from the complex mass before they could receive a definite name and character. The existing species of things having thus been transferred, with all their specialities, to the prehistoric stage, they were multiplied endlessly in number, by reducing their size through continued subdivision; at the same time each one thing is so indissolubly connected with every other that the keenest analysis can never completely sever them. The work of arrangement, the segregation of like from unlike and the summation of the omoiomere into totals of the same name, was the work of Mind or Reason; 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 Intelligence of Heraclitus, it stood pure and independent (monos ef eautou), 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. Its first appearance, and the only manifestation of it which Anaxagoras describes, is Motion. It originated a rotatory movement in the mass (a movement far exceeding the most rapid in the world as we know it), which, arising in one corner or point, gradually extended till it gave distinctness and reality to the aggregates of like parts. But even after it has done its best, the original intermixture of things is 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. The name given to it signifies merely that in that congeries of fragments the particular "seed" is preponderant. Every a of this present universe is only a by a majority, and is also in lesser number b, c, and d. 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 (sugkrisis) 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 marks a turning-point in the history of philosophy. With him speculation passed 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. By his enunciation of the order that comes from reason, on the other hand, he suggested, though he seems not to have stated explicitly, the theory that nature is the work of design. The conception of reason in the world passed from him to Aristotle, to whom it seemed the dawn of sober thought after a night of disordered dreams. From Aristotle it descended to his commentators, and under the influence of Averroes became the engrossing topic of speculation.

Socrates about Anaxagoras

Socrates in Plato's Phaedo:

“One day I heard someone reading, as he said, from a book of Anaxagoras, and saying that it is Mind (Nous) that directs and is the cause of everything. I was delighted with this cause and it seemed to me good, in a way, that Mind should be the cause of all. I thought that if this were so, the directing Mind would direct everything and arrange each thing in the way that was best. If then one wished to know the cause of each thing, why it comes to be or perishes or exists, one had to find what was the best way for it to be, or to be acted upon, or to act. On these premises then, it befitted a man to investigate only, about this and other things, what is best. The same man must inevitably know what is worse, for that is part of the same knowledge.

As I reflected on this subject I was glad to think that I had found in Anaxagoras a teacher about the cause of things after my own heart, and that he would tell me, first, whether the earth is flat or round, and then explain why it is so of necessity, saying which is better, and that it was better to be so. If he said it was in the middle of the universe, he would go on to show that it was better for it to be in the middle, and if he showed me those things I should be prepared never to desire any other kind of cause.

I was ready to find out in the same way about the sun and the moon and the other heavenly bodies, about their relative speed, their turnings, and whatever else happened to them, how it is best that each should act or be acted upon. I never thought that Anaxagoras, who said that those things were directed by Mind, would bring in any other cause for them than that it was best for them to be as they are. Once he had given the best for each as the cause for each, and the general cause of all, I thought he would go on to explain the common good for all, and I would not have exchanged my hopes for a fortune. I eagerly acquired his books and read them as quickly as I could in order to know the best and the worst as soon as possible.

This wonderful hope was dashed as I went on reading, and saw that the man made no use of Mind, nor gave it any responsibility for the management of things, but mentioned as causes air and ether and water and many other strange things...

It is what the majority appear to do, like people groping in the dark; they call it a cause, thus giving it a name which does not belong to it. That is why one man surrounds the earth with a vortex to make the heavens keep it in place, another makes the air support it like a wide lid. As for their capacity of being in the best place they could possibly be put, this they do not look for, nor do they believe it to have any divine force, but they believe that they will some time discover a stronger and more immortal Atlas to hold everything together..."

P.V. Gruji´c, Yugoslavia, THE CONCEPT OF FRACTAL COSMOS: I. ANAXAGORAS’ COSMOLOGY, Serb. Astron. J. 163 (2001), 21 – 34

Abstract: The concept of a fractal cosmos occupies a prominent position in the modern cosmology. We trace the development of this concept from the presocratic Greece to the present state of affairs. In this first part we consider the original idea due to Anaxagoras and elucidate a number of points with regard to possible interpretation of his cosmological ideas. A comparison has been made with the cosmology of Abderian school and relevance to the modern cosmology discussed.

T. Heath:

Anaxagoras, a man of science if ever there was one, was born at Clazomenae in the neighbourhood of Smyrna about 500 B.C. He neglected his possessions, which were considerable, in order to devote himself to science. Someone once asked him what was the object of being born, and he replied, "The investigation of sun, moon and heaven ". He took up his abode at Athens, where he enjoyed the friendship of Pericles. When Pericles became unpopular shortly before the outbreak of the Peloponnesian war, he was attacked through his friends, and Anaxagoras was accused of impiety for declaring that the sun was a red-hot stone and the moon made of earth. One account says that he was fined and banished ; another that he was imprisoned, and that it was intended to put him to death, but that Pericles obtained his release'; he retired to Lampsacus, where he died at the age of seventy-two.

One epoch-making discovery belongs to him, namely, that the moon does not shine by its own light but receives its light from the sun : Plato, as we have seen, is one authority for this statement. Plutarch also in his De facie in orbe lunae says, " Now when our comrade in his discourse had expounded that proposition of Anaxagoras that * the sun places the brightness in the moon,' he was greatly applauded ".

This discovery enabled Anaxagoras to say that "the obscurations of the moon month by month were due to its following the course of the sun by which it is illuminated, and the eclipses of the moon were caused by its falling within the shadow of the earth which then comes between the sun and the moon, while the eclipses of the sun were due to the interposition of the moon ". Anaxagoras was therefore the first to give the true explanation of eclipses. As regards the phases of the moon, his explanation could only have been complete if he had known that the moon is spherical ; in fact, however, he considered the earth (and doubtless the other heavenly bodies also) to be flat

To his true theory of eclipses Anaxagoras added the unnecessary assumption that the moon was sometimes eclipsed by other earthy bodies below the moon but invisible to us. In this latter assumption he followed the lead of Anaximenes. The other bodies in question were probably invented to explain why the eclipses of the moon are seen oftener than those of the sun.

Anaxagoras's cosmogony contained some fruitful ideas. According to him, the formation of the world began with a vortex set up, in a portion of the mixed mass in which " all things were together," by Mind. This rotatory movement began at one point and then gradually spread, taking in wider and wider circles. The first effect was to separate two great masses, one consisting of the rare, hot, light, dry, called the aether, and the other of the opposite categories and called air. The aether took the outer place, the air the inner. Out of the air were separated successively clouds, water, earth, and stones.

The dense, the moist, the dark and cold, and all the heaviest things, collect in the centre as the result of the circular motion, and it is from these elements when consolidated that the earth is formed. But after this, " in consequence of the violence of the whirling motion, the surrounding fiery aether tore stones away from the earth and kindled them into stars "

Anaxagoras conceived therefore the idea of a centrifugal force, as distinct from that of concentration brought about by the motion of the vortex, and he assumed a series of projections or "hurlings-off" of precisely the same kind as the theory of Kant and Laplace assumed for the formation of the solar system.

In other matters than the above Anaxagoras did not make much advance on the crude Ionian theories. " The sun is a red-hot mass or a stone on fire." " It is larger (or 'many times larger') than the Peloponnese." He considered that "the stars were originally carried round (laterally) like a dome, the pole which is always visible being thus vertically above the earth, and it was only afterwards that their course became inclined ".

But he put forward a remarkable and original hypothesis to explain the Milky Way. He thought the sun to be smaller than the earth. Consequently, when the sun in its revolution passes below the earth, the shadow cast by the earth extends without limit. The trace of this shadow on the heavens is the Milky Way. The stars within this shadow are not interfered with by the light of the sun, and we therefore see them shining ; those stars, on the other hand, which are outside the shadow are overpowered by the light of the sun which shines on them even during the night, so that we cannot see them. Aristotle easily disposes of this theory by observing that, the sun being much larger than the earth, and the distance of the stars from the earth being many times greater than the distance of the sun, the sun's shadow would form a cone with its vertex not very far from the earth, so that the shadow of the earth, which we call night, would not reach the stars at all.

Anaxagoras Moon crater
50 km diameter
2350 mt height walls
73.4N – 10.1W
In the northern lunar regions

Presocratic Philosophers series Thales | Anaximander | Anaximenes | Pythagoras | Philolaus | Archytas | Empedocles | Heraclitus | Parmenides | Zeno of Elea | Melissus | Xenophanes | Anaxagoras | Leucippus | Democritus | Protagoras | Gorgias | Prodicus | Hippias | Pherecydes