PREFACE. V 



barely excusable in a thinking age, and it is most certainly 

 not the way to disarm imposture or to put it down. If 

 the thinking and intelligent will not examine and explain 

 what is used to deceive, how can the unthinking and the 

 ignorant be but deceived, and continuously deceived, by it ? 

 Nay, we all know the experience of human weakness in 

 this respect to be such that the person whose credulity 

 has given way to deception in one case does not always, 

 where it has been rescued by explanation, resort to greater 

 caution and scepticism for the future, but, on the contrary, 

 that the idiosyncrasy of many individuals is to be deceived 

 in every instance in which competent explanation is want- 

 ing. Nor, even when caution and scepticism are produced 

 by detection of imposture, are these the great results which 

 philosophy and truth would desire to achieve. Intelligence 

 is the only bulwark of the human mind, and it is in 

 presence of this great and necessary adjunct to the integrity 

 of our normal being that the additions here made to Sir 

 David Brewster's excellent and popular work are now 

 offered to the public ; for the liability to be deceived, from 

 which we all more or less suffer, ought to be, not a 

 ground for scepticism, but only a stronger incentive to obey 

 that divine injunction : " GET KNOWLEDGE, GET WISDOM, 



AND, WITH ALL THY GETTING, GET UNDERSTANDING." 



From the nature of the case, as will be readily under- 

 stood, the eminent author's Letters have in themselves 

 been left intact, as an essential feature of their authenticity, 

 and the new matter has been introduced in the preliminary 

 and additional chapters. 



From what is explained in the succeeding chapters, it 

 will be observed that comparison is the great means by 

 which we are enabled to assure ourselves, according to 

 the existing organization of our being, of the truth or 

 falsehood of any phenomenon, and that this comparison ex- 

 tends not only to the evidence of one faculty as compared 



