[Sidenote: Diogenes asserts that air is the soul of the world.]
The doctrines of Anaximenes received a very important development in the hands of Diogenes of Apollonia, who asserted that all things originate from one essence, which, undergoing continual changes, becoming different at different times, turns back again to the same state. He regarded the entire world as a living being, spontaneously evolving and transforming itself, and agreed with Anaximenes that the soul of man is nothing but air, as is also the soul of the world. From this it follows that the air must be eternal, imperishable, and endowed with consciousness. "It knows much; for without reason it would be impossible for all to be arranged so duly and proportionately as that all should maintain its fitting measure, winter and summer, night and day, the rain, the wind, and fair weather; and whatever object we consider will be found to have been ordered in the best and most beautiful manner possible." "But that which has knowledge is that which men call air; it is it that regulates and governs all, and hence it is the use of air to pervade all, and to dispose all, and to be in all, for there is nothing that has not part in it."
[Sidenote: Difficulty of rising above fetichism.]
[Sidenote: Astronomy and chemistry have passed beyond the fetich stage.]
The early cultivator of philosophy emerges with difficulty from fetichism. The harmony observed among the parts of the world is easily explained on the hypothesis of a spiritual principle residing in things, and arranging them by its intelligent volition. It is not at once that he rises to the conception that all this beauty and harmony are due to the operation of law. We are so prone to judge of the process of external things from the modes of our own personal experience, our acts being determined by the exercise of our wills, that it is with difficulty we disentangle ourselves from such notions in the explanation of natural phenomena. Fetichism may be observed in the infancy of many of the natural sciences. Thus the electrical power of amber was imputed to a soul residing in that substance, a similar explanation being also given of the control of the magnet over iron. The movements of the planetary bodies, Mercury, Venus, Mars, were attributed to an intelligent principle residing in each, guiding and controlling the motions, and ordering all things for the best. It was an epoch in the history of the human mind when astronomy set an example to all other sciences of shaking off its fetichism, and showing that the intricate movements of the heavenly bodies are all capable not only of being explained, but even foretold, if once was admitted the existence of a simple, yet universal, invariable, and eternal law.