x PREFACE 



the value of authority as neither greater nor less, 

 than as much as it can prove itself to be worth. 

 The modern spirit is not the spirit " which always 

 denies," delighting only in destruction; still less is 

 it that which builds castles in the air rather than 

 not construct; it is that spirit which works and 

 will work "without haste and without rest," 

 gathering harvest after harvest of truth into its 

 barns and devouring error with unquenchable 

 fire. 



In the reform of philosophy, since Descartes, I 

 think that the greatest and the most fruitful re- 

 sults of the activity of the modern spirit it may 

 be, the only great and lasting results are those 

 first presented in the works of Berkeley and of 

 Hume. 



The one carried out to its logical result the 

 Cartesian principle, that absolute certainty at- 

 taches only to the knowledge of facts of conscious- 

 ness; the other, extended the Cartesian criticism 

 to the whole range of propositions commonly 

 ** taken for truth; " proved that, in a multitude of 

 important instances, so far from possessing " clear 

 ) knowledge " that they may be so taken, we have 

 ! none at all; and that our duty therefore is to 

 remain silent; or to express, at most, suspended 

 judgment. 



My earliest lesson on this topic was received 

 from Hume's keen-witted countryman Hamilton; 



