GROWTH 223 



an alarm, calling for help, whenever it was threatened 

 by hunger. In a word we oblige the plant to let us 

 know by means of conventional sounds how it thrives. 



We can now give a positive answer to the question 

 raised at the beginning of this lecture : we can not 

 only see but even hear how the plant vegetates. 

 The experiments by which we have studied the 

 various stages of the process give us at the same 

 time a clear idea of the contrivances to which we 

 must have recourse in investigating Nature. We are 

 not content with the passive part of the observer, but 

 enter into a struggle with her, during which the experi- 

 mental art offers us a whole range of tools and methods. 

 The plant is dumb, it does not answer our questions 

 we oblige it to write ; it cannot talk we oblige it to 

 ring ; somehow or other we obtain from it an answer 

 to the question raised. It is vain to look upon this 

 experimental art, as many do, as almost a mechanical 

 activity, something inferior to abstract thought. The 

 mistake was made even by the great Goethe himself. 

 In distinguishing a certain duality, a certain discord 

 between the two ways of investigating truth, between 

 theory and experiment, he made Faust speak of Nature 

 in the following way : 



' Und was sie deinem Geist nicht offenbaren mag, 

 Das zwingst du ihr nicht ab mit Hebeln und mit Schrauben.' 



Certainly it was neither lever nor press that extorted 

 the mystery from Nature it was the far-sighted medita- 

 tion and the stubborn will of the investigator that have 

 done it. The tool for investigation is as much the 

 product of a creative mind as the theory confirmed by 

 it : it is the very same thought in palpable form. Is 

 it not strange that while one might have seen for 

 centuries in almost any old city of Europe x collections 



1 In Nuremberg, for instance. 



