THE AUTHOR'S INTROSPECTIONS loi 



be borne out by evidence furnished by others — ^and this 

 to a greater extent than is necessary for other forms of 

 observation. It was hardly possible to get corroboration 

 from the other persons who had worked, with Hans, for, 

 although some of them were excellent observers of ex- 

 ternal natural phenomena, few of them had had the nec- 

 essary amount of practice in introspection. The neces- 

 sary confirmation, however, was had in laboratory tests, 

 which we shall presently describe. 



