THE GREEK ATTITUDE 



into an infinite substance which alternately generated 

 and destroyed the universe; that the pupil of this 

 philosopher, Anaximenes, returned to the doctrine of 

 Thales, merely changing the arche from water to air; 

 or that Heraclitus, the greatest of the natural phi- 

 losophers, saw in pure celestial fire and in motion the 

 unifying principles of the world. But it does signify 

 a great deal that these philosophers were the first to 

 see that matter, however diverse it may seem to our 

 senses, must have some common property, some link 

 which binds its phenomena together; this unifying 

 principle is the first intimation of what we now call 

 natural law. We, who have come to look on matter 

 as inert substance and have endued it with a separate 

 active principle which we call force or energy, can 

 get no clear conception of what they meant by water, 

 air, or fire. And they, themselves, were undoubtedly 

 quite vague in their own minds. They seem to have 

 meant that this fundamental substance changed in 

 nature from one kind of matter to another and that 

 action was brought about by moisture and heat. 



This, at least, was the opinion of Aristotle who 

 sums up the ideas of the school of Natural Philoso- 

 phers as follows: "Thales, the founder of this school 

 of philosophy, says the principle is water, getting the 

 notion perhaps from seeing that the nutriment of all 

 things is moist, and that heat itself is generated from 

 the moist and kept alive by it (and that from which 

 they come to be is a principle of all things). He got 



C 39 3 



