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

92
IMMEDIATE INFERENCE.
alone, is applied in the predicate to the whole of the
class (P) of which the subject forms only a part. The
determinant is, therefore, not the same in the two
cases, inasmuch as its reference or application is differ
ent. If the phraseology is so guarded as to maintain
the identity of reference, the validity of the inference
cannot be challenged, whatever may be thought of
its usefulness. The inferred propositions, in the two
examples given, would then require to be read, "All
incompetent kings are men who are incompetent as
"
kings j
"A huge cottage is a building which is huge
for a cottage."
Immediate Inference by Complex Conception is a
process essentially similar; it is subject to the same
and is valid under the
danger from verbal ambiguity,
same precautions. The process consists in employing
the subject and predicate of the original proposition as
parts of a more complex conception e.g.,
"A horse is
a quadruped," therefore "The head of a horse is the
"
head of a quadruped." But from All Protestants are
"
"
Christians we cannot infer that A majority of Protes
tants are a majority of Christians," but only that they
constitute a majority of Protestant Christians.
Immediate Inference by Converse Relation is the
name given by Mr Keynes to a process by which, from
a statement of the relation in which P stands to Q, we
pass to a statement of the relation in which Q conse
quently stands to P. "
Thus, from P is greater than
"
"
"
Q we infer immediately, Q is less than P from
;
"
" "
A B is younger than A from
is older than B,"
"A is the father of B,"
" " X is equal to Y Y,"
"
"B is the child of A ;
"
is equal to X and so on.
;
;
from
The two terms of the original proposition are transposed,