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THE AMERICAN NATURALIST [Vol. XL VII 



cases do occur, the question whether entelechy is to be 

 brought in is a non-experimental one. 



4. Relation op Eadically Experimental Analysis to 

 Other Formulations 



Radically experimental analysis thus reduces all ques- 

 tions to an experimental situation; seeks for every ex- 

 isting perceptual difference between cases to find a pre- 

 ceding perceptual difference on which the later one 

 experimentally depends; and results in a formulation or 

 explanation which includes only perceptual factors. 



We often find, particularly in biology, formulations 

 or explanations which are based on non-perceptual fac- 

 tors. This non-perceptual character is not always real- 

 ized, nor readily detectible; it will be brought out by 

 applying to the doctrine in question the two rules set 

 forth above. In other cases the formulation confessedly 

 includes non-perceptual factors; such is the vitalism of 

 Driesch. 



For clear thinking as to all such doctrines, confessed 

 or unconfessed, a grasp of their relations to radically ex- 

 perimental analysis is essential. The crucial questions 

 are: Can radically experimental analysis be carried 

 through all parts of science, even biology? That is, can 

 experimental causes be found for all that occurs? If so, 

 are other sorts of causes likewise required? Is recourse 

 to formulations including non-perceptual factors due to 



(1) a supposed lack of experimentally perceptible de- 

 termining differences for all differences in results; or 



(2) to a mental need for some other conditions, in addi- 

 tion to the perceptual ones, to show perhaps "why" the 

 perceptual conditions produce the results they do? 

 Supplementary non-perceptual theories of the first sort, 

 based on an assumed lack of perceptual determining 

 factors, tend to discourage experimentation or the search 

 for perceptual determining factors; while supplemen- 

 tary theories of the second sort have nothing to do with 

 experimental science. 



April 18, 1913 



