Xviii. PROLEGOMENA. 



by the sensorium to the mind, without the presence 

 of external causes, and caused by some internal 

 activity of parts. Suppose a man, subject to 

 Ih^se illusions, or after a fever, should see a 

 golden sphere in the room before him ; and a 

 second person standing in the room, who of 

 course did not see it, should hear him make the 

 assertion ; he would first try this visionary's 

 troth by his own trotli, and say, " No, it cannot 

 be so, for I cannot see it :" both might contend 

 for the truth ; and as here was one man's assertion 

 against another, and as one man might have a 

 defect of vision, or the other might have a 

 redundancy of imagery, the only appeal that 

 could be made, would be to a third. The third 

 man agreeing with the second, the spectrum 

 would be condemned as illusive or wanting truth. 

 . If the visionary still persisted in his assertion, 

 then others v>ould be applied to, and so on, till 

 the general consensus being obtained, the illusive 

 character of the spectrum would be established. 

 In ordinary cases the patient would now give up 

 the point, and take medicine or exercise to cure 

 himself. But where a fixed and insurmountable 

 adherence to the belief of the spectrum were 

 persisted in, the patient would be deemed a 

 maniac. And indeed I take the being possessed 

 of illusive sensations, and at the same time not 

 being aware of their nature, and refusing to 



