ii THE CONTENTS OF THE MIND 77 



Hume has been criticised for making the 

 distinction of impressions and ideas to depend 

 upon their relative strength or vivacity. Yet it 

 would be hard to point out any other character by 

 which the things signified can be distinguished. 

 Any one who has paid attention to the curious 

 subject of what are called " subjective sensations " 

 will be familiar with examples of the extreme 

 difficulty which sometimes attends the discrimi- 

 nation of ideas of sensation from impressions of 

 sensation, when the ideas are very vivid, or the 

 impressions are faint. Who has not "fancied" 

 he heard a noise; or has not explained inattention 

 to a real sound by saying, " I thought it was noth- 

 ing but my fancy " ? Even healthy persons are 

 much more liable to both visual and auditory 

 spectra that is, ideas of vision and sound so vivid 

 that they are taken for new impressions than is 

 commonly supposed; and, in some diseased states, 

 ideas of sensible objects may assume all the vivid- 

 ness of reality. 



If ideas are nothing but copies of impressions, 

 arranged, either in the same order as that of the 

 impressions from which they are derived, or in a 

 different order, it follows that the ultimate 

 analysis of the contents of the mind turns upon 

 that of the impressions. According to Hume, 

 these are of two kinds: either they are impres- 

 sions of sensation, or they are impressions of 

 reflection. The former are those afforded by the 



