374 NATURE AND MAN. 



first framed the conception — and his vast mathematical ability, 

 which enabled him to give it definite shape — that the moon is 

 constantly " falling " towards the earth at a rate exactly conform- 

 able to that " law " of terrestrial gravitation, with which the name 

 and fame of Galileo will ever be associated. 



My own first ideas of the Newtonian Philosophy, if I rightly 

 remember, were drawn from the answer given in that best child's 

 book of my generation — "Evenings at Home" — to the question 

 "Why does an apple fall?" Whether the apple of Newton is to 

 be relegated, like that of Tell, to the limbo of " myths," is a question 

 I shall not stop to discuss. It is enough that the story .serves to 

 illustrate the "idea." Probably if the question were put to a 

 hundred "educated" people, ninty-nine of them would give one of 

 these two answers, "Because of the earth's attraction," or, " Because 

 of the law of gravitation." But, as I have shown, to speak of the 

 attraction of the earth, is merely to express, in different words, the 

 fact that it " draws " the apple downwards ; and if we go further 

 and say that the earth draws downwards not only apples, but 

 stones, water, and air — in fact, all material bodies whatever — we 

 only express a general uniformity, of which we know nothing more 

 than that it is. Clearly it is no real "explanation" of the fall of 

 any one apple, to say that all apples or all material bodies fall 

 when unsupported. So the " law " of gravitation is merely an 

 expression of that general uniformity, framed with a scientific 

 exactness which enables us to say " with certainty " (in common 

 parlance) what will be the time occupied in the fall of a heavy body 

 through any given number of feet. But that "certainty" depends 

 not upon any " governing " action of the " law " itself, — for into the 

 purely scientific conception of law the idea of a governing power 

 does not enter ; — but solely upon our rational expectation that 

 what has been found conformable to a vast experience in the past, 

 under every variety of conditions, will in like manner prove con- 

 formable to it in the future. 



Before, however, we follow the development of Galileo's 

 doctrine of terrestrial gravitation into the Newtonian doctrine of 

 universal gravitation, we must deal with another of the "laws" 

 imposed on Nature by the ancient philosophy. It was held that 

 as a circle is the most "perfect " figure, and as the motions of the 



