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

54
THE LOGICAL PROPOSITION.
universal proposition, so called because the predicate
is affirmed or denied of every instance of the subject,
the reference is to
in
"
the whole of the subject." Thus,
"
All planets shine by reflected this light," quality is
affirmed of each of the class of
"
planets," although it is
not strictly true as a scientific fact ; and in
" No
men
are utterly bad," this quality is denied of each one of the
"
class human If it is not beings." already in the form
"
or No S is the P," proposition, if it is
"
"
All S is P
really universal, can be expressed in this form without
altering its meaning.
(<:) The affirmation or denial may be made of a part
of a certain class. In this case the proposition is said
to be particular. Its logical form is
"
"Some S is not P :
"
"
some men are born great ;
" Some
S is P
"some statesmen are not practical."
The particular proposition, in ordinary language, is an
assertion about some quantity between these two
extremes, that in which the predicate is affirmed of the
whole of the subject, and that in which it is denied of
the whole i.e., it means "some only," "only a 1
part."
But in its logical form the particular proposition only
excludes
it does not exclude the possibility of
"
"
none ;
the reference to
and there may or may
"
all." In other words, it means "
"
not be more or all
at least." The only possible ground for taking
i.e.,
"
"
"
or
some,
some
"
some
in the former, the narrower, sense, in a logical proposi
tion, is our knowledge of its subject-matter, not anything
in the formal expression of the proposition :
"
some
1 In ordinary language this convention is so strict that the word
"some" is of itself sufficient to deny "all" : "All men are to be
bought
"
"
bought.
may be denied by the simple
statement "some are to be