54 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



deal only with such phenomena as occur on bodies in nature, 

 called organisms, and that it will be our purpose to discover 

 the laws according to which the motions of these bodies 

 occur. We may end in vitalism again in this chapter ; 

 but certainly we shall not end in pseudo-psychology. 



General Definition of Action. Classes of Movements 



which are not Actions 



A few remarks about the most general definition of 

 action, in both a positive and a negative form, seem 

 desirable by way of preliminary. 



An " action " is every animal movement which depends 

 for its specificity on the individual life history of its 

 performer in such a manner that this specificity depends 

 not only, as will be seen later on, on the specificity of the 

 actual stimulus but also on the specificity of all stimuli in 

 the past, and on their effect. No animal movement is to 

 be called an action in which this criterion is not present 

 at least in a certain degree. In the language of subjective 

 psychology this criterion is called " experience." We shall 

 presently introduce a more suitable name for it, but in 

 this short survey the word " experience " may be used. 



There is no experience, and therefore no " action," when 

 the final physiological elemental process in the motor 

 organs, i.e. the process of contraction, goes on better the 

 second or third than it did the first time : we speak of 

 " functional adaptation " of the nervous system 1 in this 



1 Functional adaptation of the muscles as such is, of course, another 

 phenomenon, not belonging to the present discussion. 



