SUPERFICIAL APPEARANCES A SOURCE OF ERROR. 113 



larity, but of causation ; the relationship of cause and effect 

 is of a more fundamental nature than that of similarity ; 

 the chief principle of the great plan of nature, which we 

 should endeavour to represent in our minds, is not that 

 of collections of similar things, but of unity in diversity, 

 and the two combine, by the great principle of causation, 

 to form a harmonious whole. This is the idea, by means 

 of the development of which, the mind of man is most 

 truly converted into a correct image of the great Cause 

 of all things. Nature is much less truly represented by 

 collections of similar things than by branching series of 

 different but related ones. 



Another source of error is absence of systematic 

 arrangement of ideas. This may usually be remedied by 

 proper classification ; i.e. writing them down singly and 

 separately, dividing them into suitable groups, selecting 

 the most important ones for treatment first, and arranging 

 the ideas of each class in such a manner that those which 

 precede shall include those which follow. Another cause 

 is want of attention or concentration of thought, and this 

 itself is often caused by absence of mental discipline, and 

 often also by the intrusion of the cares of life or other ideas 

 upon the attention. No man can understand a subject, 

 and especially discover new scientific truths which tax his 

 utmost intellectual powers, whilst other ideas are forced 

 upon his notice. Another cause, though not a common 

 one in original research, is the use of wrong terms ; the 

 cure for this is to select the right ones, which may usually 

 be done by the aid of suitable books, such as dictionaries, 

 glossaries of terms, books of synonyms, &C. 1 The clear 

 proposition of a problem, or the precise statement of a 

 question or hypothesis, is often of greater importance than 



1 Koget's Thesaurus of Words and Phrases is a good book for such 

 a p-arpose. 



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