INTRODUCTION. XV 



hand the kind of information already acquired, and on the 

 other that which is still desirable or desiderated. 



Designed originally to form a single volume of the In- 

 ternational Scientific Series, I have found it impossible, 

 after fruitless efforts at condensation, to compress what 

 must be said in such a preliminary treatise within the com- 

 pass of one volume of 300 or 400 pages. With the con- 

 currence, therefore, on the one hand of the publishers, and 

 on the other of the committee of the International Scientific 

 Series of books, instead of issuing an incomplete work by 

 the omission of what I regard as its most important half 

 that which treats of mental disease I have been constrained 

 to cast the whole materials in two volumes, treating re- 

 spectively of the varied phases or phenomena on the one 

 hand of healthy, and on the other of diseased, mind. 



Anxious as far as possible, in a work intended for 

 popular use, to divest the subject of mind in animals of 

 all unnecessary, repulsive, or confusing technicalities, I have 

 purposely used the term mind itself, and all terms relating 

 to its constituents or operations, in their ordinary, popular, 

 or comprehensive sense. All men of experience and culture 

 feel, rather than know, what these terms express or imply, 

 though it has been abundantly shown, by the frequent un- 

 successful attempts that have been made, how impossible it is 

 to define them satisfactorily. Indeed, no two authors agree 

 as to the signification that should be attached to such terms 

 as 'will,' 'feeling/ 'thought,' 'consciousness,' 'intention/ 

 and so forth. So far as I can judge, after a special study of 

 several of the fashionable modern systems of psychology 

 of mental or moral philosophy such as those of Herbert 

 Spencer and Professor Bain, I do not think anything would 

 be gained by attempting, in such a work as the present, the 

 strict definition of these or similar terms, or their restricted 

 use, solely in a metaphysical, psychological, or other purely 

 scientific or technical sense. I do not, therefore, here at- 

 tempt psychological definition or classification, preferring to 

 permit each reader to define and classify according to his own 

 favourite system of nomenclature and arrangement. 



I do not venture to generalise beyond a certain safe limit ; 



