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SCIENCE 



[N. S. Vol. XXXIII. No. 859 



produce fundamental changes in the prin- 

 ciples of experimentation. This is the point 

 which, to me as an experimenter, seems 

 hardly to receive adequate consideration by 

 Professor Lovejoy; this appears to me the 

 reason why this particular kind of vitalism 

 (the vitalism of Driesch) has received so 

 much attention from investigators, though as 

 a rule they are rather indifferent to vitalistie 

 theory. This is the vitalism which holds that 

 the laws of what occurs in organisms " can 

 not even be stated in terms of the number and 

 arrangement of the organism's physical com- 

 ponents.'" This statement means, if it means 

 anything, that you can not make a statement 

 which will hold, that a given arrangement of 

 physical components will act in a certain 

 definite way (even after you have observed 

 how it acts). If such a statement will not 

 hold, this can be only because the same ar- 

 rangement of physical components acts some- 

 times in one way, sometimes in another — so 

 that there results indeterminism so far as the 

 physical components are concerned.* If vital- 

 ism of this sort is correct, then the biologist 

 can not from a knowledge of the total physical 

 configuration predict what will happen, even 

 after he has observed it. 



To realize the situation in which this leaves 

 the experimenter, it is needful to consider just 

 what his work consists in. The experimental 

 investigator is engaged in discovering the de- 

 termining causes of things. Just what we are 

 to understand by cause has given rise to much 

 discussion, often leading far away from any 

 experimental concept.^ Experimentally it 



^ Lovejoy, I. c. 



* A natural result of this is to do what Driesch 

 does and "what Lovejoy seems inclined to depre- 

 cate; to assume the existence of some non -physical 

 factor, as enteleehy, to supply the missing differ- 

 ential determining condition. This grows out of 

 the ordinary procedure in experimental investiga- 

 tiom; whether it really helps the experimenter in 

 his work we shall inquire in a moment. 



'■ The ambiguities in the word cause have in- 

 duced some investigators to drop it entirely, and 

 deal only with words having no implication that is 

 not definable in experimental terms; so Verworn 

 in the fifth edition of his ' ' General Physiology. ' ' 



means any preceding event or condition with- 

 out which the event we are studying would 

 not have occurred. Now it turns out in ex- 

 perimentation that everything has a very 

 great number of such " causes," all standing 

 on the same experimental footing, so that to 

 determine " the cause " of any event, taken 

 by itself, is a hopeless task; so taken, the 

 meaning of cause becomes nndefinable, unless 

 it could be held to signify finding out eveiy- 

 thing that must have happened in order that 

 this event may occur. Progress can be made 

 only when we so state our problem that we 

 need search for but one determining cause at 

 a time. Now, one single sufficient experi- 

 mental cause can he found only for the dif- 

 ference hetween two cases, and the actual 

 practise of experimental investigation consists 

 in comparing two cases and finding experi- 

 mentally what determines the difference be- 

 tween them; discovering, that is, what pre- 

 ceding difference results experimentally in 

 producing the present difference. 



An example will make this clear. An or- 

 ganism is observed to move over a certain 

 stretch, from a to h. What is the cause of 

 this? The question so put opens up a vast 

 perspective; we may go into the production of 

 the energy which brings about the movement, 

 with the infinite number of questions that this 

 involves; we may study the special organs by 

 which this organism performs its movements, 

 and how these organs were produced; we may 

 take up the stimuli which set the organism in 

 motion, and those which determine its direc- 

 tion; the environmental conditions on which 

 the motion depends, etc. All biological sci- 

 ence is before us; where shall we take hold? 

 We must make our question precise, and this 

 can be done by considering two differing cases. 

 This specimen now swims in a certain direc- 

 tion; this other (or this same one at a differ- 

 ent time) in a different direction. What is 

 the cause of this difference? A little experi- 

 mentation shows that the one, only and suffi- 

 cient cause is the different direction of the 

 rays of light in the two cases. Or, again, this 

 specimen swims in a certain direction, while 



