IV PREFACE. 



conciliating the principles of the Art with as much as is well- 

 grounded in the doctrines and objections of its assailants. 



The same abstinence from details could not be observed in the 

 First Book, on Names and Propositions ; because many useful 

 principles and distinctions which were contained in the old Logic, 

 have been gradually omitted from the writings of its later teachers ; 

 and it appeared desirable both to revive these, and to reform and 

 rationalize the philosophical foundation on which they stood. The 

 earlier chapters of this preliminary Book will consequently appear, 

 to some readers, needlessly elementary and scholastic. But those 

 who know in what darkness the nature of our knowledge, and of 

 the processes by which it is obtained, is often involved by a con- 

 fused appz'ehension of the import of the different classes of Words 

 and Assertions, will not regai'd these discussions as either frivolous, 

 or irrelevant to the topics considered in the later Books. 



On the subject of Induction, the task to be performed was that 

 of generalizing the modes of investigating truth and estimating 

 evidence, by which so many important and recondite laws of 

 nature have, in the various sciences, been aggregated to the stock 

 of human knowledge. That this is not a task free from difficulty 

 may be presumed from the fact, that even at a very recent period, 

 eminent writers (among whom it is sufficient to name Archbishop 

 Whately, and the author of a celebrated article on Bacon in the 

 Edinburgh Review), have not scrupled to pronounce it impossible. 

 The author has endeavored to combat their theory in the manner 

 in which Diogenes confuted the skeptical reasonings against the 

 possibility of motion ; remembering that Diogenes' argument would 

 have been equally conclusive, although his individual perambula- 

 tions might not have extended beyond the circuit of his own tub. 



Whatever may be the value of what the author has succeeded 

 in effecting on this branch of his subject, it is a duty to acknowledge 

 that for much of it he has been indebted to several important trea- 

 tises, partly historical and partly philosophical, on the generalities 

 and processes of physical science, which have been published within 

 the last few years. To these treatises, and to their authors, he has 

 endeavored to do full justice in the body of the work. But as with 

 one of these writers, Mr. Whewell, he has occasion frequently to 

 express differences of opinion, it is more particularly incumbent on 

 him in this place to declare, that without the aid derived from the 

 facts and ideas contained in that gentleman's History of the Induc- 

 tive Sciences, the corresponding portion of this work would probably 

 not have been written. 



