A HISTORY OF SCIENCE 



the other is intended to transcend the bounds of the 

 natural. That is to say, both are concerned with the 

 sequence of actual events, with the observation of 

 actual phenomena; but the modern observer has the 

 almost infinite advantage of being able to draw upon 

 an immense store of careful and accurate observations. 

 A knowledge of the mistakes of his predecessors has 

 taught him the value of caution in interpreting phe- 

 nomena that seem to fall outside the range of such 

 laws of nature as experience has seemed to demon- 

 strate. Again and again the old metaphysical laws 

 have been forced aside by observation ; as, for example, 

 when Kepler showed that the planetary orbits are not 

 circular, and Galileo's telescope proved that the spot- 

 bearing sun cannot be a perfect body in the old Aristo- 

 telian sense. 



New means of observation have from time to time 

 opened up new fields, yet with all the extensions of our 

 knowledge we come, paradoxically enough, to realize 

 but the more fully the limitations of that knowledge. 

 We seem scarcely nearer to-day to a true understanding 

 of the real nature of the "forces '' whose operation we 

 see manifested about us than were our most primitive 

 ancestors. But in one great essential we have surely 

 progressed. We have learned that the one true school 

 is the school of experience; that metaphysical causes 

 are of absolutely no consequence unless they can gain 

 support through tangible observations. Even so late 

 as the beginning of the nineteenth century, the great 

 thinker, Hegel, retaining essentially the Greek cast of 

 thought, could make the metaphysical declaration that, 

 since seven planets were known, and since seven is the 



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