508 
PROFESSOR JEVONS ON THE MECHANICAL 
To investigate the proper mode of treating this condition, we may take the same series 
of eight conceivable combinations and raise those containing a , in order to separate the 
excluded combinations. But it is not now sufficient simply to lower such of the included 
combinations as contain b , and condemn these as inconsistent with the premise. For 
though these combinations do not contain B they may contain C, and may require to he 
admitted as consistent on account of the second alternative of the predicate. While the 
AB’s are certainly to be admitted, the AZ>’s must he subjected to a new process of selec- 
tion. Now the simplest mode of preparing for this new selection is to join the AB’s to 
the a’s or excluded combinations, to move up the A &’s into the place last occupied by 
the A’s, to lower such of the A b ' s as do not contain C. The result will then be as 
follows : — 
Excluded combinations and included (A. A 
combinations consistent with 1st B B 
alternative [C c 
Included combination inconsistent with Is 
but consistent with 2nd alternative . . 
Included combination inconsistent with both 
natives 
It is only the lowest rank of combinations, in this case containing only A be, which 
is inconsistent with the premise as a whole, and which is therefore to be condemned as 
contradictory ; and if we join the two higher ranks we have effected the requisite analysis. 
29. It will be apparent that should the subject of the premise contain a disjunctive 
conjunction, as in 
A or B is C, 
a similar series of operations would have to be performed. We must not merely raise 
the as and treat them as excluded combinations, but must return them to undergo a 
new sifting, whereby the a B’s will be recognized as included in the meaning of the 
subject, and only the a b's will be treated as excluded. This analysis effected, the 
remaining operations are exactly as before. 
30. The reader will perhaps have remarked that in the case of none of the premises 
considered has it been requisite to separate the combinations of the abecedarium into 
more than four groups or ranks, and it may be added that all problems involving simple 
logical relations only have been sufficiently represented by the examples used. The 
task of constructing a mechanical logic is thus reduced to that of classifying a series of 
wooden rods representing the conceivable combinations of the abecedarium into certain 
definite groups distinguished by their positions, and providing such mechanical arrange- 
ments, that wherever a letter term occurs in the subject or predicate of a proposition, 
a a a a 
B B b b 
C c C c 
