The Doctrine of Air
For Anaximenes the primary source of all things is air. He held that at one time everything in fact was air, and that it has changed due to natural forces in constant motion to alter it into the other substances which came together to form the world. This is largely due to early Greek literature in which air is associated with the soul. (the breath of Life). Anaximenes thought the air was capable of directing its own development as the body directs the soul. In the one fragment attributed directly to Anaximenes, he writes
Air is the nearest to an immaterial thing; for since we are generated in the flow of air, it is necessary that it should be infinite and abundant, because it is never exhausted.
The Doctrine of Change
By using two contrary processes, rarefication and condensation, Anaximenes explains that air is part of a process of a series of changes. Fire turns to air, then air transforms to wind. This in turn forms clouds, which turns to rain, falling to the earth where it transforms to stone. Likewise, if we heat the stone with fire, it transforms back into air. This theory of change becomes distinct, because he backs it up with observation. Aristotle writes
Plut. Prim. Frig. vii. 3, p. 947. According to Anaximenes, the early philosopher, we should not neglect either cold or heat in being but should regard them as common experiences of matter which are incident to its changes. He says that the compressed and the condensed state of matter is cold, while the rarefied and relaxed (a word he himself uses) state of it is heat. Whence he says it is not strange that men breathe hot and cold out of the mouth; for the breath is cooled as it is compressed and condensed by the lips, but when the mouth is relaxed, it comes out warm by reason of its rarefaction.
The Soul
Anaximenes argues that the soul is like air in its nature. It is the source of life that encloses the cosmos and is responsible for maintaining all living things. As the soul (air) of the individual maintains its life, so the soul of the cosmos (the universal breath) maintains the universe. To this end, Anaximenes perceives the cosmos as a huge animate being with divine origins.
Cic. de Nat, Deor. i. 10; Dox. 531. Afterwards Anaximenes said that air is god,4 [and that it arose] and that it is boundless and infinite and always in motion; just as though air without any form could be god, when it is very necessary that god should be not only of some form, but of the most beautiful form; or as though everything which comes into being were not thereby subject to death.
The Origin of the Cosmos
Anaximenes gives us an account of how the world came to be out of previously existing matter. The Earth was formed by air as it compressed, in the shape of a flat disk. As the earth evaporated, fiery bodies arose to become heavenly bodies. The Earth floats on a stream of air, as likewise do the sun and moon. The heavens are like a felt cap that turns around the head, the stars fixed to this surface like nails.
Anaximenes also uses these principles to explain other natural phenomena. Lightning and thunder are from wind breaking out of the clouds, rainbows from rays of sun falling on the clouds. Earthquakes are caused by when the earth dries out and cracks, or becomes wet and crumbles. hail is frozen rainwater.
Hipp. Philos. 7; Dox. 560 ...the form of air is as follows:—When it is of a very even consistency, it is imperceptible to vision, but it becomes evident as the result of cold or heat or moisture, or when it is moved. It is always in motion; for things would not change as they do unless it were in motion....
the broad earth is supported on air; similarly the sun and the moon and all the rest of the stars, being fiery bodies, are supported on the air by their breadth. And stars are made of earth, since exhalations arise from this, and these being attenuated become fire, and of this fire when it is raised to the heaven the stars are constituted....
the sun is hidden not by going underneath the earth, but because it is covered by some of the higher parts of the earth, and because of its greater distance from us. The stars do not give forth heat because they are so far away. Winds are produced when the air that has been attenuated is set in motion; and when it comes together and is yet farther condensed, clouds are produced, and so it changes into water. And hail is formed when the water descending from the clouds is frozen; and snow, when these being yet more filled with moisture become frozen; and lightning, when clouds are separated by violence of the winds; for when they are separated
