MODE OF FORMING NEW HYPOTHESES. 369 



sf testing new questions are often invented in a similar 

 manner, viz., by associating with them the idea of some 

 sontrivance which, in somewhat different form, has already 

 3een used in some other department of science. The 

 more apparently unlike or remote the two ideas are, the 

 greater probably in all cases is the mental effort required 

 :o associate them together, because it is difficult to 

 magine simultaneously conceptions which are unlike. 

 The continuity of development of new scientific know- 

 .edge through all time (like the continuity of living 

 species), and consequently also the continuity of human 

 progress, is likewise partly secured by means of this 

 mental marriage process, because if we could not imagine 

 new hypotheses, we could not suggest an explanation of 

 any new fact or phenomenon, and much of our new 

 scientific knowledge would be almost unattainable. It is 

 evident from these remarks that close study and searching 

 criticism and comparison of scientific truths are most 

 :ffectual means of exciting the scientific imagination to 

 raise new questions. It is a useful plan to keep a 

 classified record of those questions and ideas, and peruse 

 them occasionally ; by this means additional ones are 

 suggested. From the collection thus obtained, the more 

 promising ones may be copied into a separate book, and 

 from these a suitable subject of research may at any time 

 be selected. 



The power, activity, and variety of the imagination 

 may be considerably increased by practising the formation 

 of hypotheses, in the manner already described, on every 

 available opportunity. This practice may be greatly 

 assisted by the use of a table of classified series of leading 

 ideas of the various sciences, and associating each of these 

 ideas in succession with that of the phenomenon under 

 consideration, and then forming questions respecting it by 



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