II THE CONTENTS OF THE MIND 75 



the most he, or anybody else, can prove in favour 

 of his conclusion is, that we know nothing more 

 of the mind than that it is a series of perceptions. 

 Whether there is something in the mind that 

 lies beyond the reach of observation ; or whether 

 perceptions themselves are the products of some- 

 thing which can be observed and which is not 

 mind ; are questions which can in nowise be 

 settled by direct observation. Elsewhere, the 

 objectionable hypothetical element of the defini- 

 tion of mind is less prominent : 



1 The true idea of the human mind is to consider it as a 

 system of different perceptions, or different existences, which 

 are linked together by the relation of cause and effect, and 

 mutually produce, destroy, influence and modify each other. . . . 

 In this respect I cannot compare the soul more properly to 

 anything than a republic or commonwealth, in which the 

 several members are united by the reciprocal ties of government 

 and subordination, and give rise to other persons who propa- 

 gate the same republic in the incessant changes of its parts." 

 (I. p. 331). 



But, leaving the question of the proper defini- 

 tion of mind open for the present, it is further a 

 matter of direct observation, that, when we take 

 a general survey of all our perceptions or states of 

 consciousness, they naturally fall into sundry 

 groups or classes. Of these classes, two are 

 distinguished by Hume as of primary importance, 

 All "perceptions," he says, are either "Impres- 

 sions " or " Ideas." 



Under " impressions " he includes " all our more 



