PERCEPTION 99 



first without the intermediary of /^-operators, and second 

 through 5-operators ; then by a comparison of the two he 

 could determine the laws according to which B-operators 

 work. But this is just what he cannot do, since he cannot 

 get outside of his own organism. And if he wished to deter- 

 mine the way in which M-operators act he would be obliged 

 to get an object in the 13-context, first without the inter- 

 mediary of M-operators, and second through M-operators; 

 then by a comparison of the two he could determine how 

 M-operators work. This, again, he cannot do, since he 

 cannot get outside of his own mind. Hence, since one cannot 

 learn the laws of the operators he cannot use such laws as a 

 foundation for inferring from objects in one context to 

 objects in another. 



Though this difficulty cannot, perhaps, be avoided the- 

 oretically, it can be and is avoided practically. This is done 

 through the notion of normal operators. One decides, more 

 or less arbitrarily, that a certain type of situation may be 

 defined as a normal observational situation. Psychologically, 

 such a situation would be defined as one in which the ob- 

 server is attentive, deliberate, free from prejudices and pre- 

 conceptions, and without emotional biases. A situation of 

 this kind can be empirically distinguished from one in 

 which the designated attributes are lacking. Biologically, a 

 normal observational situation would be one in which the 

 observer is in possession of sense organs which have met 

 certain specified tests. These tests are, of course, compara- 

 tive in character and assure one only that the individual in 

 question, as indicated by the verbal responses which he 

 makes when he is presented with varying objects, can make 

 distinctions where the majority of individuals make dis- 

 tinctions, and fails to find differences where the majority 

 of individuals fail to find them. Physically, a normal ob- 

 servational situation would be one in which the object is at 

 the proper distance from the sense organ, in which there 

 are no intervening recording instruments, and in which 

 the unavoidable media such as fight, atmosphere, and electro- 



