196 THE PRINCIPLES OF SCIENCE. [CHAP. ix. 



between a certain number of logical terms, we also meet 

 a case of higher combinations. We have seen (p. 145) that 

 with only six terms the number of possible selections of 

 combinations is 18,446,744,073.709,551,616. Considering 

 that it is the most common thing in the world to use an 

 argument involving six objects or terms, it may excite 

 some surprise that the complete investigation of the 

 relations in which six such terms may stand to each 

 other, should involve an almost inconceivable number 

 of cases. Yet these numbers of possible logical relations 

 belong only to the second order of combinations. 



