THE PRINCIPLES OF PRAGMATISM 125 



as in the behavior of vegetable organisms, to which we 

 hesitate to ascribe consciousness. Such facts, however, need 

 not lead us to modify the general proposition that the survi- 

 val-value of consciousness consists in its enabling the organism 

 to learn. And, practically speaking, the ability to learn is the 

 only test by means of which the presence of consciousness in 

 any organism can be demonstrated. 



The most elementary form of the learning-process, and that 

 which furnishes a general type for all the more complicated forms 

 may be succinctly described as follows. If the mode of behavior 

 which is modified by the learning-process be called habit (the 

 term being used in its widest sense, including instinctive be- 

 havior), then, conversely, the primary function of consciousness 

 may be described as the modification of habit. The inadequacy 

 or inappropriateness of habitual response, from which the activity 

 of consciousness upon any occasion takes its rise, is evidenced by 

 an unpleasant feeling. And the readjustment in which the task 

 of consciousness finds its accomplishment is marked by a feeling 

 of pleasure, which, however, vanishes as the readjustment be- 

 comes complete. The task of consciousness may be described 

 as the forming of a distinction between the stimulus which has 

 normally provoked a certain response, and a second stimulus, 

 which so far resembles the first as originally to elicit the same 

 response, but with unpleasant effects. The task is accomplished 

 when this latter stimulus has acquired its own peculiar satis- 

 factory response, following it invariably and without confusion; 

 whereupon consciousness gradually disappears. Thus, speaking 

 generally, we may say that consciousness becomes active, only 

 as it becomes necessary in order to eke out the inadequacy of 

 existing modes of reaction where its peculiar survival value 

 comes into play. So long as the habit serves, consciousness exists, 

 if at all, only as a vanishing quantity. 



The phrase, "the forming of a distinction," which we have 

 used, is ambiguous, or rather has a double meaning. The learn- 

 ing-process is at once the development of behavior and the 



