IMAOINATIOK 47 



whicli will therefore acquire greater vividness ; while the four differing 

 impressions of each will not only acquire no greater strength than they 

 had at first, but, in accordance with the law of association, they will 

 all tend to appear at once, and will thus neutralize one another, 



"This mental operation may be rendered comprehensible by consid- 

 ering what takes place in the formation of compound photographs — 

 when the images of the faces of six sitters, for example, are each re- 

 ceived on the same photographic plate, for a sixth of the time requisite 

 to take one portrait. The final result is that all those points in which 

 the six faces agree are brought out strongly, while all those in which 

 they differ are left vague ; and thus what may be termed a generic \)ov- 

 trait of the six, in contradistinction to a specific portrait of any one, is 

 produced. 



" Thus our ideas of single complex impressions are incomplete in 

 one way, and those of numerous, more or less similar, complex im- 

 pressions are incomplete in another way ; that is to say, they are gen- 

 eric, not specific. And hence it follows that our ideas of the impres- 

 sions in question are not, in the strict sense of the word, copies of those 

 impressions ; while, at the same time, they may exist in the mind in- 

 dependently of language. 



" The generic ideas which are formed from several similar, but not 

 identical, complex experiences are what are called abstract or general 

 ideas ; and Berkeley endeavored to prove that all general ideas are 

 nothing but particular ideas annexed to a certain term, which gives 

 them a more extensive signification, and makes them recall, upon oc- 

 casion, other individuals which are similar to them. Hume says that 

 he regards this as ' one of the greatest and the most valuable discover- 

 ies that has been made of late years in the republic of letters,' and en- 

 deavors to confirm it in such a manner that it shall be ' put beyond 

 all doubt and controvei'sy. ' 



"I may venture to express a doubt whether he has succeeded in his 

 object ; but the subject is an abstruse one ; and I must content my- 

 self with the remark, that though Berkeley's view appears to be largely 

 applicable to such general ideas as are formed after language has been 

 acquired, and to all the more abstract sort of conceptions, yet that gen- 

 eral ideas of sensible objects may nevertheless be produced in the way 

 indicated, and may exist independently of language. In dreams, one 

 sees houses, trees, and other objects, which are perfectly recognizable as 

 such, but which remind one of the actual objects as seen ' out of the 

 corner of the eye,' or of the pictures thrown by a badly- focussed magic 

 lantern. A man addresses us who is like a figure seen in twilight ; or 

 we travel through countries where every feature of the scenery is vague ; 

 the outlines of the hills are ill-marked, and the rivers have no defined 

 banks. They are, in short, generic ideas of many past impressions of 

 men, hills, and rivers. An anatomist who occupies himself intently 

 with the examination of several specimens of some new kind of animal, 

 in course of time acquires so vivid a conception of its form and struc- 



