270 PSYCHOLOGY. 



measure to be let into his neighbor's mind and to find now 

 different the scenery there was from that in his own. 



Thought is in fact a kind of Algebra, as Berkeley long ago 

 said, "in which, though a particular quantity be marked by 

 each letter, yet to proceed right, it is not requisite that iu 

 every step each letter suggest to your thoughts that par- 

 ticular quantity it was appointed to stand for." Mr. Lewes 

 has developed this algebra-analogy so well that I must 

 quote his words : 



" The leading characteristic of algebra is that of operation on rela- 

 tions. This also is the leading characteristic of Thought. Algebra can- 

 not exist without values, nor Thought without Feelings. The operations 

 are so many blank forms till the values are assigned. Words are va- 

 cant sounds, ideas are blank forms, unless they symbolize images and 

 sensations which are their values. Nevertheless it is rigorously true, 

 and of the greatest importance, that analysts carry on very extensive 

 operations with blank forms, never pausing to supply the symbols with 

 values until the calculation is completed; and ordinary men, no less 

 than philosophers, carry on long trains of thought without pausing to 

 translate their ideas (words) into images. . . , Suppose some one from 

 a distance shouts ' a lion ! ' At once the man starts in alarm. . . . 

 To the man the word is not only an . . . expression of all that he has 

 seen and heard of lions, capable of recalling various experiences, but is 

 also capable of taking its place in a connected series of thoughts without 

 recalling any of those experiences, without reviving an image, however 

 faint, of the lion — simply as a sign of a certain -relation Included in the 

 complex so named. Like an algebraic symbol it may be operated on 

 without conveying other significance than an abstract relation : it is a 

 sign of Danger, related to fear with all its motor sequences. Its logical 

 position suffices. . . . Ideas are substitutions which require a secondary 

 process when what is symbolized by them is translated into the images 

 and experiences it replaces; and this secondary process is frequently not 

 performed at all, generally only performed to a very small extent. Let 

 anyone closely examine what has passed iu his mind when he has con- 

 structed a chain of reasoning, and he will be surprised at the fewness 

 and faintness of the images which have accompanied the ideas. Sup- 

 pose you inform me that ' the blood rushed violently from the man's 

 heart, quickening his pulse at the sight of his enemy.' Of the many la- 

 tent images in this phrase, how many were salient in your mind and in 

 mine ? Probably two — the man and his enemy — and these images were 

 faint. Images of blood, heart, violent rushing, pulse, quickening, and 

 sight, were either not revived at all, or were passing shadows. Had 

 any such images arisen, they would have hampered thought, retarding 

 the logical process of judgment by irrelevant connections. The symbols 

 had substituted relatiotis for these values. . . . There are no images of 



