276 THE METAPHYSICS OF SENSATION 



interposition of units of sensibility, or minima 

 sensibilia, is an idea common to the two. And 

 whether I see a point move across the field of vision 

 towards another point, or feel the like motion, the 

 idea of the gradual diminution of the number of 

 sensible units between the two points appears to 

 me to be common to both kinds of motion. 



Hence, I conceive, that though it be true that 

 there is no likeness between the primary feelings 

 given by sight and those given by touch, yet there 

 is a complete likeness between the secondary 

 feelings aroused by each sense. 



Indeed, if it were not so, how could Logic, 

 which deals with those forms of thought which 

 are applicable to every kind of subject-matter, be 

 possible ? How could numerical proportion be as 

 true of visibilia, as of tangibilia, unless there were 

 some ideas common to the two ? And to come di- 

 rectly to the heart of the matter, is there any more 

 difference between the relations between tangible 

 sensations which we call place and direction, and 

 those between visible sensations which go by the 

 same name, than there is between those relations 

 of tangible and visible sensations which we call 

 succession ? And if there be none, why is Geo- 

 metry not just as much a matter of visibilia as of 

 tangibilia ? 



Moreover, as a matter of fact, it is certain that 

 the muscular sense is so closely connected with 

 both the visual and the tactile senses, that, by 



