3 66 ELEMENTS OF SCIENCE 



observation and of inference, and inference plays a 

 yet larger part in many historical investigations. 



But we may occupy ourselves not with what may be 

 the truth in this or that scientific inquiry, but about the 

 different kinds of truth attainable in different inquiries. 

 The sort of truth to be gained by the study of the 

 geometry of Euclid is evidently different in nature 

 from that afforded by investigations as to animal physio- 

 logy.* This leads us to the question of the different 

 degrees of truth which different inquiries may be able to 

 afford us, and so we may pass on from considering what 

 are the tests to be applied, and their value, in different 

 branches of knowledge, to the question whether there is 

 any one test we can apply to the ultimate and funda- 

 mental propositions of every branch of knowledge ; and 

 if so, what that one test may be ? 



Thus the various sciences have each their own funda- 

 mental truths which are vouched for and shown to be 

 valid by their own proper tests. But we should endeavour 

 to see whether there are any truths which underlie all 

 sciences, and if so what they are, and what, if anything, 

 vouches for them and establishes their validity. 



In this chapter, then, we propose to introduce the 

 student to a knowledge of the elements of " Science par 

 excellence " and to consider what, if any, test can be 

 found, not for truths of this or that order, but for all 

 truths of whatsoever order. 



In this consideration we shall have to make use of 

 reasoning, as we have again and again made use of it, 

 and no science can be properly followed up without the 

 aid of reasoning. 



Now we all know that science has greatly advanced 



* See ante, p. 187. 



