Preface to the First Edition. xi 



of evidence, what are the ultimate foundations upon which its 

 rules rest, what the nature of the evidence they are capable 

 of affording, and to what class of subjects they may most fitly 

 be applied. That the science of Probability, on this view of 

 it, contains something more important than the results of a 

 system of mathematical assumptions, is obvious. I am con 

 vinced moreover that it can and ought to be rendered both 

 interesting and intelligible to ordinary readers who have any 

 taste for philosophy. In other words, if the large and grow 

 ing body of readers who can find pleasure in the study of 

 books like Mill s Logic and Whe well s Inductive Sciences, 

 turn with aversion from a work on Probability, the cause in 

 the latter case must lie either in the view of the subject or 

 in the manner and style of the book. 



I take this opportunity of thanking several friends, 

 amongst whom I must especially mention Mr Todhunter, of 

 St John s College, and Mr H. Sidgwick, of Trinity College, 

 for the trouble they have kindly taken in looking over the 

 proof-sheets, whilst this work was passing through the Press. 

 To the former in particular my thanks are due for thus 

 adding to the obligations which I, as an old pupil, already 

 owed him, by taking an amount of trouble, in making sug 

 gestions and corrections for the benefit of another, which few 

 would care to take for anything but a work of their own. 

 His extensive knowledge of the subject, and his extremely 

 accurate judgment, render the service he has thus afforded 

 me of the greatest possible value. 



GONVILLE AND CAIUS COLLEGE, 



September, 1866. 



