462 SPECIAL METHODS OF DISCOVERY. 



by intentional, reproduced it, and the analysis was found 

 to be correct, whilst the synthesis is now daily performed 

 for commercial purposes.' ' By the mutual co-operation, 

 then, of these two processes, the physical sciences are 

 advanced. If no attempts were made to draw a conclusion 

 and see what use could be made of it till grounds formally 

 complete were before us, conclusions would never be drawn. 

 The certainties by which the chemist, the astronomer, the 

 geologist, conducts his operations with composure and 

 success, were once bare possibilities, which, after being 

 handed backward and forward between Induction and 

 Deduction, turned out to be truths.' 1 



Any method of successfully using the human faculties 

 in effecting a scientific discovery depends upon several 

 conditions : 1 . and chiefly, upon the actual and possible 

 constitution of external nature ; 2. upon the capabilities 

 of our mental and physical powers ; 3. upon the kind of 

 discovery to be effected ; and 4. upon the state of natural 

 knowledge at the time. The empirical rules based upon 

 these conditions are, that we must not attempt to discover 

 contradictions of the laws of nature, that we must consider 

 the limits of our faculties, that we must adapt the means 

 to the end, and that we must not try to discover truths 

 which are insufficiently ripe. 



1 . With regard to the dependence of the method upon 

 external nature, it is manifest, from universal experience, 

 that although we cannot discover anything which actually 

 contradicts the laws of nature, we may discover not only 

 what explicitly exists, but a multitude of substances and 

 actions which do not so exist, but which agree with and 

 are implicitly or potentially contained in the great prin- 

 ciples of science, and are therefore capable of explicit 



1 Thomson, Outline of the Lam of Thought, pp. 238, 239. 



