10 HISTORY OF INDUCTIVE SCIENCES. 



progress from one principle to another, different 

 and often apparently contradictory. Now, it is im- 

 portant to remember that this contradiction is ap- 

 parent only. The principles which constituted the 

 triumph of the preceding stages of the science, may 

 appear to be subverted and ejected by the later 

 discoveries, but in fact they are, (so far as they 

 were true,) taken up into the subsequent doctrines 

 and included in them. They continue to be an 

 essential part of the science. The earlier truths 

 are not expelled but absorbed, not contradicted but 

 extended ; and the history of each science, which 

 may thus appear like a succession of revolutions, is, 

 in reality, a series of developements. In the intel- 

 lectual, as in the material world, 



Omnia mutantur nil interit 



Nee manet ut fuerat nee form as servat easdem, 

 Sed tamen ipsa eadem est. 



All changes, nought is lost; the forms are changed, 

 And that which has been is not what it was, 

 Yet that which has been is. 



Nothing which was done was useless or unessential, 

 though it ceases to be conspicuous and primary. 



Thus the final form of each science contains the 

 substance of each of its preceding modifications; 

 and all that was at any antecedent period dis- 

 covered and established, ministers to the ultimate 

 developement of its proper branch of knowledge. 

 Such previous doctrines may require to be made 

 precise and definite, to have their superfluous and 



