A HISTORY OF SCIENCE 



it, is in itself a supposition seemingly contradicted by 

 ordinary experience. It required the mind of a phi- 

 losopher, sustained, perhaps, by some experimental ob- 

 servations, to conceive the idea that what seems so 

 obviously bright may be in reality dark. The germ 

 of the conception of what the philosopher speaks of 

 as the noumena, or actualities, back of phenomena 

 or appearances, had perhaps this crude beginning. 

 Anaxagoras could surely point to the moon in support 

 of his seeming paradox that snow, being really com- 

 posed of water, which is dark, is in reality black and 

 not white a contention to which we shall refer more 

 at length in a moment. 



But there is yet another striking thought connected 

 with this new explanation of the phases of the moon. 

 The explanation implies not merely the reflection of 

 light by a dark body, but by a dark body of a particu- 

 lar form. Granted that reflections are in question, 

 no body but a spherical one could give an appear- 

 ance which the moon presents. The moon, then, is 

 not merely a mass of earth, it is a spherical mass 

 of earth. Here there were no flaws in the reasoning 

 of Anaxagoras. By scientific induction he passed 

 from observation to explanation. A new and most 

 important element was added to the science of as- 

 tronomy. 



Looking back from the latter-day stand-point, it 

 would seem as if the mind of the philosopher must 

 have taken one other step: the mind that had con- 

 ceived sun, moon, stars, and earth to be of one sub- 

 stance might naturally, we should think, have reached 

 out to the further induction that, since the moon is a 



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