THE LOGICAL MACHINE. 



125 



hand side, or as it used to be called the predicate of the 

 proposition, the letter keys on the right-hand side of the 

 keyboard are the proper representatives. The five other 

 keys may be called operation keys, to distinguish them 

 from the letter or term keys. They stand for the stops, 

 copula, and disjunctive conjunctions of a proposition. The 

 middle key of all is the copula, to be pressed when the 

 verb is or the sign = is met. The extreme right-hand 

 key is called the Full Stop, because it should be pressed 

 when a proposition is completed, in fact in the proper 

 place of the full stop. The extreme left-hand key is 

 used to terminate an argument or to restore the machine 

 to its initial condition ; it is called the Finis key. The 

 last key but one on the right and left complete the 

 whole series, and represent the conjunction or in its un- 

 exclusive meaning, or the sign -|- which I have employed, 

 according as it occurs in the right or left hand side 

 of the proposition. The whole keyboard is arranged 

 as shown below 



To work the machine it is only requisite to press the 

 keys in succession as indicated by the letters and signs 

 of a symbolical proposition. All the premises of an ar- 

 gument are supposed to be reduced to the simple notation 

 which has been employed in the previous pages. Taking 

 then such a simple proposition as 



A = AB, 



we press the keys A (subject), copula, A (predicate), 

 B (predicate), and full stop. 



