68 



which is capable of but one other variety, namely, 

 A - B iiot-C or not-BC. 



Each of these propositions can be expressed in six apparently 

 different modes, which on examination are found to have 

 exactly the same logical meaning. 



A complete solution of the problem of three terms having 

 been obtained, it is pointed out that the corresponding 

 problem for four terms is almost impracticable, since it 

 would involve the detailed examination of Qo,5S6 different 

 selections of combinations. The problem of five terms may 

 be called impossible as regards complete solution, since it 

 involves no less than 4,294,967,296 cases. Similarly, six 

 terms admit of more than eighteen trillions of cases. Thus 

 it is quite impossible that the complete solution of the 

 inverse logical problem should ever be carried more than 

 one step further than it has been done in this paper. 



