An introductory text-book of logic - Mellone, Sydney - Rare Books at ...

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CONDITIONAL ARGUMENTS AND
similar arguments to syllogistic form, by making the
principle or axiom on which they depend into a major
premise :
"Things equal to the same thing are equal to one
another ;
A and B are equal to the same thing ;
Therefore A and B are equal to one another."
It is replied that this is not a true syllogism because
the whole argument is contained in the major premise ;
and that in any case it does not represent the given
argument, for C does not appear in it.
(b) Relations of
time and space also frequently give rise to reasonings
which appear to be not :
syllogistic
" Bacon lived before
Locke, Locke lived before Hume, therefore Bacon lived
before Hume"; "A is north of B, B is north of C,
therefore A is north of C."
In the formal syllogism the copula of the propositions
originally expressed only the relation of subject and
attribute ; and though (as we have seen) it easily ex
presses the relation of genus and species (class inclusion
and exclusion), it does not naturally express all possible
relations. Hence Professor De Morgan proposed to
extend the meaning of the copula, to take it merely
as a general symbol signifying some kind of relation
between subject and predicate ; so that the typical
form :
syllogism would take the following
A is related to B in a certain understood way ;
En ii C in the same way ;
.\A n H C in that way.
This proposed extension of the meaning of the copula
has been called the Logic of Relatives. Dr Martineau
had already (1852) suggested a classification of such
relations :
" The ideas of space and time, of cause and