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is true under every circumstance and condition; for 

 otherwise, it could be both true and false. We need 

 not therefore be afraid of comparing truth with truth, 

 under whatever shape it may arrive, as though it were 

 possible that either of its phases could ever suffer from 

 the ordeal of a close contact ; since, if they be really 

 true, and free from deception, they must needs go hand 

 in hand, and may become (however opposite they be in 

 their subjects) directly explanatory of each other. The 

 astronomer who is not intimately acquainted with pure 

 mathematical analysis, in its various aspects and 

 bearings, is in fact no astronomer at all. The geologist 

 who would interpret the grand phenomena of the earth's 

 crust apart from statical and dynamical knowledge, and 

 without the help which the chemist, mineralogist, 

 anatomist, zoologist, and botanist can afford him, stands 

 a fair chance of leaving his problems unsolved ; whilst 

 the students of zoology and botany who would endeavour 

 to understand, and account for, what they see in the 

 animal and vegetable worlds around them, without 

 calling in geology to their aid, must assuredly be pre- 

 pared to fail signally in their attempts. All indeed 

 must work in concert, if the whole is to be advanced,- 

 and not only in concert, but as mutually assisting each 

 other. "By the help of truths already known, more 

 may be discovered; for those inferences which arise 

 from the application of general truths to the particular 

 things and cases contained under them, must be just.* ; 

 * Religion of Nature Delineated, pp. 73, 74. 



