PEEFACE TO THE THIED AND FOUETH 

 EDITIONS. 



SEVERAL criticisms, of a more or less controversial 

 character, on this work, have appeared since the pub- 

 lication of the second edition ; and Dr. Whewell has 

 lately published a reply to those parts of it in which 

 some of his opinions were controverted.* 



I have carefully reconsidered all the points on 

 which my conclusions have been assailed. But I 

 have not to announce a change of opinion on any 

 matter of importance. Such minor oversights as 

 have been detected, either by myself or by my 

 critics, I have, in general silently, corrected : but 

 it is not to be inferred that I agree with the objec- 

 tions which have been made to a passage, in every 

 instance in which I have altered or cancelled it. I 

 have often done so, merely that it might not remain 

 a stumbling-block, when the amount of discussion 

 necessary to place the matter in its true light would 

 have exceeded what was suitable to the occasion. 



To several of the arguments which have been 

 urged against me, I have thought it useful to reply 

 with some degree of minuteness ; not from any taste 



* Now forming a chapter in his volume on The Philosophy 

 of Discovery. 



