2 2o POPULAR SCIENCE MONTHLY 



tent of the thought, I have the further consciousness that I have already 

 had this thought, that it is familiar to me. 



Similar, though somewhat more complicated, is the phenomenon in 

 the case of experiences in which the external world had participated. 

 After eating an apple, I may repeat this experience in two ways. I 

 may repeat it as an inner experience, though with diminished intensity. 

 Another part, the sensations that formed a piece of my experience, I 

 am unable at will to reproduce in myself; but am compelled again to 

 eat an apple in order to have a similar experience in this respect as 

 well. This is a complete repetition that it is not necessarily in my 

 power to produce because it is essential that I have an apple, i. e., that 

 certain conditions belonging to the external world and independent of 

 myself be fulfilled. 



Whether in the repetition of an experience the outer world takes 

 part or not has no influence upon the content of consciousness, called 

 ' memory/ It follows, therefore, that the latter belongs wholly to in- 

 ternal experience, and that we remember an external event only 

 through its inner constituents. The mere repetition of corresponding 

 sense impressions is not sufficient. We may see the same individual 

 repeatedly without recognizing him in case the accompanying inner 

 phenomena have, through lack of interest, been so slight that their 

 repetition does not produce this content of consciousness, ' memory.' 

 If, however, we see him very often, the frequent repetition of the ex- 

 ternal impression finally produces the memory of the inner experience 

 that goes with it. 



Hence it follows that to call forth the reaction, ' memory,' a defi- 

 nite intensity of the internal experience is necessary. This threshold 

 value may be attained either at one time by one strong impression, or 

 by numerous repetitions of weak ones. The repetitions are the more 

 effective, the more rapidly they follow upon one another. Hence we 

 may conclude further that the memory value of an experience, or its 

 power upon repetition to call forth the reaction, ' memory,' diminishes 

 in the course of time. 



Furthermore we must take into consideration the above-mentioned 

 fact that a completely accurate reproduction of an experience never 

 takes place. The reaction, ' memory,' must therefore be called forth 

 when in place of complete correspondence there is merely similarity or 

 partial correspondence. Here, too, there are gradations. Memory ap- 

 pears the more easily, the more completely the two experiences cor- 

 respond; and vice versa. 



If we look at these relations from a physiological point of view, we 

 are able to say: We possess two kinds of contrivances or organs, of 

 which one is independent of, and the other dependent upon, our will. 

 The former are the organs of sense, the latter is the organ of thought. 



