Died: 428 B.C
The last of the great Ionian philosophers and a philosopher of nature known for his cosmology and for his discovery of the cause of eclipses was born in the seventh Olympiad (about 500 B.C. ) at Clazomenae (or Klazomene), Lydian coast of Asia Minor (near present-day Smyrna) (now Turkey) in an aristocratic family and died in the first year of the eighty-eighth Olympiad (428), according to the chronicles of Appollodros. Anaxagoras son of Hegesiboulos, moved to Athens in about 480 and spent most of his life there.
To devote himself to science and philosophy, he gave up his property and moved to Athens, then becoming the center of Greek culture. Anaxagoras had the honor of giving philosophy a home at Athens where it flourished for a thousand years. He was an intimate friend of the Athenian statesman Pericles and the writer of tragedies Euripides. Anaxagoras moved in good company. He was a part of the brilliant circle of artists, sculptors, architects, musician, and poets that Pericles gathered about himself. He began to teach philosophy in the archonship of Kallias at Athens (480).
He wrote on book "On Nature", according to Diogenes and the same authority says that this was written in the Ionic dialect, of which only fragments are preserved. Anaxagoras started from the "what is" (see Parmenides) and postulated a plurality of elements which he called 'seeds' (see Empedocles). As a follower of the old Milesian school he tried to revive the thoughts of Anaximenses in the post-Parmenidean period. He is agreed with Empedocles that all coming into and going out of being consists merely in the mixture and separation of already existing substances. There are infinite number combination of elements of different shape, color, and taste. Later writers referred to the 'seeds' as omoiomereia (from an expression of Aristotle). Everything is infinite in number and infinitesimally small. If they were put together, they lose their distinction because of infinitesimally. In other words because of smallness they can not be distinct. On the other end of the spectrum, air and aether comprehended all things. Both aether and air are present everywhere, they are infinite in sizes and numbers. The air and aether are separated from the surrounding (mass), which is infinite. Before the separation of things nothing was clear, even there was not any color or distinct things like, moist, dry, warm, cold, bright, dark etc. The rotation of the things that were moved made already distinct things more distinct. Earth is condensed out of the things that are separated. For water is separated from the clouds, and earth from the water; and from the earth stones are condensed by cold; and these are separated farther from water. Things in the one universe are not divided form each other neither hot from cold nor cold from hot. That is, everything is infinitely divisible and that even the smallest portion of matter contains some of everything. For example, snow has black too but it looks white because of white dominance. Everything contains everything else. The color, size, shape, taste, etc. all depend on the quantities and combinations of different things in it.
Towards the end of his life (just before the Peloponnesian War), however, he got into trouble. The Athenians were conservative in matters religious, and in this respect differed from the liberal, freethinking, tolerant Ionian Greeks. Pericles himself was accused of being pro-Ionian and un-Athenian. The opposition used Anaxagoras philosophical system (and his Milesian mistress) against Pericles. In his book, Anaxagoras had declared that the sun was not a god, but a piece of fiery stone about the size of the Peloponnesus. The moon, too, was not as goddess but was made of earth and had plains and ravines in it and reflected the Sun’s light. Russell writes, “The citizens of Athens…passed a law permitting impeachment of those who did not practice religion and taught theories about ‘the things on high’. Under this law they persecuted Anaxagoras, who was accused of teaching that the sun was as red-hot stone and the moon was earth”. For these assertions, he tried for blasphemy, convicted, and thrown into prison. He escaped, however, and fled back to Ionia. He settled at Lampsacus, Mysia (now Turkey) where he died in 428 B.C. at the age of seventy two.
He is considered be the last major Greek philosopher. As Cohen writes, “After Pythagoras Anaxagoras of Clazomenae dealt with many questions in geometry…” He was a philosopher of nature remembered for his cosmology and for his discovery of the true cause of eclipses. One should examine this work on cosmology especially about the sun. There are remarkable insights in this account. The idea of differentiation of matter (which plays a large role in modern theories of creation of the solar system is present) and understanding of centrifugal force shows the extra ordinary scientific insights that he possessed. There is also other indication to imply that Anaxagoras had applied geometry to the study of astronomy.