Information about Anaxagoras and his works is incomplete and contradictory. Only fragments of his book on natural history survive; most of these are quoted in the seventh century c.e. writings of Simplicius, who may have quoted them from another source. Others assert that Anaxagoras’ book was lost as early as the third century b.c.e. In addition to these fragmentary texts, Aristotle and Plato describe Anaxagoras’ concepts and philosophy. From these sources, several contrasting versions of Anaxagoras’ works have been constructed. Despite inconsistencies, a general understanding of Anaxagoras’ contributions to the philosophy of science does exist.
Anaxagoras’ treatise on natural philosophy became a standard text in ancient Athens. In contrast to earlier Greek thinkers, he postulated an infinite number of fundamental elements in the universe, rather than one or a few elements. He also asserted that nous, or mind, created the cosmos. According to Anaxagoras, nous first formed all of the elements by a process of mixing and revolving. Thus all of “the dark” came together to form the night, all “the fluid” formed the ocean, and all other elements formed similarly. During a second stage flesh and other elements were brought together by nous to create living things. Because ethical concerns are not addressed in Anaxagoras’ cosmology, it was later criticized by Aristotle and Plato. However, this omission and Anaxagoras’ scientific inquiries—such as his discovery of the true cause of eclipses—make him the earliest known natural philosopher, or true scientist.
Around 480 b.c.e. Anaxagoras moved to Athens, where he probably remained for thirty years. While there he attracted a “school” and was accepted in the highest circles. Pericles was one of his students and openly acknowledged his indebtedness to Anaxagoras. Aristotle based part of his work on that of Anaxagoras, some of whose teachings were inserted into drama, either seriously or as subjects for lampoon. Around 433-430 b.c.e., Anaxagoras was prosecuted by Cleon for impiety and atheism. Anaxagoras’ statement that the sun was an incandescent stone somewhat larger than the Peloponnese Peninsula was given as the reason for his prosecution; however, it is thought that the prosecution was actually an attack upon Pericles. Pericles was able to save Anaxagoras’ life, but could not prevent his exile. Thereafter Anaxagoras resided at Lampsacus where he reestablished his school and continued his work until his death.