8 GREAT MEN OF SCIENCE 



This is not the case; they merely resumed and carried on a 

 method which had been begun, but then allowed to go to 

 waste, or merely to revolve around uncreative changes. Even 

 Aristotle, mentally distorted as he was, had made observa- 

 tions. When for example, he states that light bodies fall 

 more slowly than heavy ones, he had without doubt observed 

 the fall of feathers and stones. Stevin and Galileo certainly 

 went about their work in a different manner from Aristotle, 

 since they again took seriously both the multiplicity and also 

 the quantitative aspect of observation; but Pythagoras had 

 already expressly pointed this out, and Archimedes and 

 Hipparchus had acted in the same manner. Stevin, Galileo, 

 and the great men who followed them, were certainly very 

 different from Aristotle with his hasty generalisations and 

 easy certainty; but in this respect also they were only like 

 their true forerunners. They passed only gradually from 

 observation of what offered itself directly to them, to an in- 

 creasing degree of true experiment; that is to say, to carrying 

 out observations under carefully thought-out and favourable 

 conditions, and with the assistance of specially constructed 

 appliances. In this way, Galileo arrived at his experiment 

 with the fall of bodies on the inclined plane and his observa- 

 tions of the heavens by means of the telescope; but Archi- 

 medes had also experimented when he immersed various 

 bodies in water. 



The progress of the new epoch as compared with 

 the old therefore consists only in the gradually in- 

 creasing and intentional multiplication and refinement of 

 observation, and in the increasing use made of conditions 

 intentionally arranged for the production of the phenomena 

 to be observed; as for example, when Galileo investigated 

 the movements of pendulums swinging with different arcs, 

 or constructed of different lengths. This was not essentially 

 different from the procedure of Archimedes when he varied 

 the length of the arms of the lever, or imagined them as 



