Anaxagoras of Clazomenae

Greek philosopher, born c.500 BC (Clazomenae, Turkey), died c.428 BC, Lampsacus (dates attested by Diogenes Laertius¹)

Anaxagoras, with the other Presocratic philosophers, was one of the founders of the Western philosophical tradition.

Biography

Unless otherwise stated, the source of Anaxagoras' biography, philosophy and cosmology is Diogenes Laertius¹. Between about 463-433 Anaxagoras was in Athens, and taught Pericles and Euripides. "He became something of an archetypal wise man (calm in the face of the death of his son), and also an atheistic scientist figure (calm in the face of a solar eclipse)"².

But he was prosecuted for impiety by Pericles’ political opponents. Anaxagoras had deemed the purpose of life to be 'the investigation of the Sun, the Moon, and the heavens³.  But this gave Pericles' enemies an excuse to attack him. Not being able to make a direct political assault, they prosecuted him for suggesting the Sun and the stars were hot stones, and not gods. Pericles saved him, but he was forced to retire to Lampsacus.

Philosophy and Cosmology

Only fragments of Anaxagoras' writings have survived, so it is difficult to produce a coherent account of the details of his philosophy. But there is enough to gain an outline understanding of the main lines of his thought.

Early Greek thinkers thought of the universe as being composed of one element. Parmenides asserted that such an assumption could not account for movement and change. Empedocles posited four elements, but Anaxagoras posited an infinite number.

Anaxagoras suggested almost every distinguishable thing was an element - like flesh, bone, bark, and leaf. He suggested that the universe was formed by "Mind". First the night was created, then the oceans, and then all other elements.

The elements were initially formed into an undifferentiated mass of stuffs. These were stirred into rotary motion by the active principle of Mind. Different stuffs separated out into bodies like our Earth.  In the final stage, biological elements were brought together by Mind to form life. Unlike Empedocles, Anaxagoras did not consider the future evolution of the world or give a vision of its end or infinite progression. Barnes⁴ gives a more detailed account of his cosmological theory.

Anaxagoras also investigated more basic astronomical matters. This work was probably more fruitful than his more speculative cosmology. For instance, he claimed the moon was illuminated by reflected sunlight. Aristarchus used this idea to indicate how the distance to Sun might be calculated. Simon Singh has a good account of this procedure in his excellent popular work on cosmology³.

References

[1] Diogenes Laertius, Lives of the Philosophers, II.7-10.

[2]The First Philosophers: The Presocratics and Sophists, trans. Robin Waterfield (Oxford: Oxford University Press, 2000)

[3]Big Bang by Simon Singh (Fourth Estate, October 2004)

[4]Jonathan Barnes, The Presocratic Philosophers (London: Routledge, 1989), p.320