THE ART OF SCIENTIFIC INVESTIGATION 



to one without the other person having said a word. The same 

 may happen during the delivery of a lecture, for when the 

 teacher explains something he "sees" it more clearly himself 

 than he had before. The other person, by asking questions, even 

 ill-informed ones, may make the narrator break the established 

 chain, even if only to explain the futiUty of the suggestion, and 

 this may result in him seeing a new approach to the problem or 

 the connection between two or more observations or ideas that 

 he had not noticed before. The effect that questioning has on 

 the mind might be Ukened to the stimulus given to a fire by 

 poking ; it disturbs the settled arrangement and brings about new 

 combinations. In disturbing fixed Hnes of thought, discussion is 

 perhaps more likely to be helpful when carried on with someone 

 not familiar with your field of work, for near colleagues have 

 many of the same thought habits as yourself The writing of a 

 review of the problem may prove helpful in the same way as 

 the giving of a lecture. 



A further useful application of the conception of conditioned 

 thinking is that when a problem has defied solution it is best 

 to start again right from the beginning, and if possible with a 

 new approach. For example, I worked unsuccessfully for several 

 years trying to discover the micro-organism which causes foot-rot 

 in sheep. I met with repeated frustrations but each time I started 

 again along the same lines, namely, trying to select the causal 

 organism by microscopy and then isolating it in culture. This 

 method seemed the sensible one to follow and only when I had 

 exhausted all possibilities and was forced to abandon it, did I 

 think of a fundamentally different approach to the problem, 

 namely, to try mixed cultures on various media until one was 

 found which was capable of setting up the disease. Work along 

 these lines soon led to the solution of the problem. 



SUMMARY 



Productive thinking is started off by awareness of a difficulty. 

 A suggested solution springs into the mind and is accepted or 

 rejected. New combinations in our thoughts arise from rational 

 associations, or from fancy or perhaps chance circumstances. The 

 fertile mind tries a large number and variety of combinations. 



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