242 Mr Dugald Stewart on Ventriloquism. 



In what follows, I take for granted that my readers are ac- 

 quainted with the distinction, so finely illustrated by Bishop 

 Berkeley, between the original and the acquired perceptions of 

 our different senses ; more particularly, between the original 

 and the acquired perceptions of the eye and of the ear. It is 

 on the former of these senses that Berkeley has chiefly enlar- 

 ged ; and this he has done with such a fulness and clearness 

 of illustration, that succeeding writers have in general done 

 nothing more than to repeat over his reasonings, with very 

 little, either of alteration or of addition. The metaphysical 

 problems relating to the sense of hearing have been hitherto 

 overlooked by almost all our physiologists, although they pre- 

 sent various subjects of inquiry, not less curious and difficult 

 than those connected with the theory of vision. 



The senses of hearing and of seeing agree in this, that they 

 both convey to us intimations concerning the distances, and 

 also concerning the directions of their respective objects. The 

 intimations, indeed, which we receive by the former, are by no 

 means so precise as those of the latter. They are, however, 

 such as to be of essential use to us in the common concerns of 

 life. That one sound comes from the immediate neighbour- 

 hood, — another from a distance ; one sound from above, — 

 another from below ; one from before, — another from behind ; 

 one from the right hand, — another from the left, are judgments 

 which we have every moment occasion to form, and which 

 we form with the most perfect confidence. 



With respect to the signs which enable us to form our esti- 

 mates of distance by the ear, there is little or no difficulty ; as 

 they seem to consist merely of the different gradations of which 

 sounds are susceptible in point of loudness and of distinctness. 

 In what manner our estimates of direction are formed, has not 

 I think, been as yet satisfactorily explained ; nor, indeed, do 

 I know of any writer whatever, excepting Mr Gough of Ken- 

 dal, who has even attempted the solution of the problem. The 

 difficulty attending it arises, probably, in some measure, from 

 the imperfection of our knowledge concerning the theory of 

 sound ; a subject which, after all the researches of Sir Isaac 

 Newton, continues to be involved in considerable obscurity. 

 One thing seems to be pretty obvious, that the effect of which 



