74 



Historical Methods 



attract the reader's attention to various possibilities of error, of which he might be 

 unaware. It is well to study or to read one of those guides from time to time, as 

 one's experience and caution increase. ' Experience is necessary but insufficient. 

 One's critical sense should be periodically resharpened. Moreover, one's knowl- 

 edge of valuable tools is never complete, not only because new tools are published 

 almost every year, but also because no matter how diligent a scholar may be there 

 are always some ancient tools which he managed to overlook. I have realized this 

 more than once to my mortification. 



