TACTILK JUDGMENTS 439 



bhe table with the finger, take a round lead pencil 

 between the fingers, and draw that along the table. 

 The "sensation" of a flat hard surface will be just as 

 clear as before ; and yet all that we touch is the round 

 surface of the pencil, and the only pure sensations we 

 owe to the table are those afforded by the muscular sense. 

 In fact, in this case, our " sensation " of a flat hard surface 

 is entirely a judgment based upon what the muscular 

 sense tells us is going on in certain muscles. 



A still more striking case of the tenacity with which 

 we adhere to complex judgments, which we conceive to 

 be pure sensations, and are unable to analyse otherwise 

 than by a process of abstract reasoning, is afforded by our 

 sense of roundness. 



Any one taking a marble between two fingers will say 

 that he feels it to be a single round body ; and he will 

 probably be as much at a loss to answer the question how 

 he knows that it is round, as he would be if he were asked 

 how he knows that a scent is a scent. 



Nevertheless, this notion of the roundness of the 

 marble is really a very complex judgment, and that it is 

 so may be shown by a simple experiment. If the index 

 and middle fingers be crossed, and the marble placed 

 between them, so as to be in contact with both, it is 

 utterly impossible to avoid the belief that there are two 

 marbles instead of one. Even looking at the marble, 

 and seeing that there is only one, does not weaken 

 the apparent proof derived from touch that there are 

 two.i 



The fact is, that our notions of singleness and round- 

 ness are, really, highly complex judgments based upon 

 a few simple sensations ; and when the ordinar}' conditions 

 of those judgments are reversed, the judgment is also 

 reversed. 



1 A ludicrous form of this experiment is to apply the crossed fingers to 

 the end of the nose, when it at once appears double; and in spite of 

 the absurdity of the conviction the mind cannot expel it so long as the 

 •eusations last. 



