INTRODUCTION. 1 1 



arbitrary portions expunged, to be expressed in new 

 language, to be taken up into the body of science 

 by various processes; but they do not on such 

 accounts cease to be true doctrines, or to form a 

 portion of the essential constituents of our know- 

 ledge. 



Terms record Discoveries. The modes in which 

 the earlier truths of science are preserved in its 

 later forms, are indeed various. From being as- 

 serted at first as strange discoveries, such truths 

 come at last to be implied as almost self-evident 

 axioms. They are recorded by some familiar maxim, 

 or perhaps by some new word or phrase, which 

 becomes part of the current language of the philoso- 

 phical world ; and thus asserts a principle, while it 

 appears merely to indicate a transient notion; 

 preserves as well as expresses a truth ; and, like a 

 medal of gold, is a treasure as well as a token. 

 We shall frequently have to notice the manner in 

 which great discoveries thus stamp their impress 

 upon the terms of a science ; and, like great poli- 

 tical revolutions, are recorded by the change of the 

 current coin which has accompanied them. 



Generalization. The great changes which thus 

 take place in the history of science, the revolutions 

 of the intellectual world, have, as a usual and lead- 

 ing character, this, that they are steps of generali- 

 zation; transitions from particular truths to others 

 of a wider extent, in which the former are included. 

 This progress of knowledge, from individual facts 



