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

102 IMPORT OF PROPOSITIONS AND JUDGMENTS.
extension without their intension, is to make "
"
S is P
into a form of words which says nothing. 1
The five forms, to which the class view naturally leads,
are further removed from the meaning of our ordinary judg
ments than the traditional four forms, even when the latter
are also interpreted by the class view. For in common
thought we frequently do not know whether the whole
extent of the predicate is to be referred to or not ; but the
fivefold division supposes us to know in every case whether
all or only part of the predicate is referred to. Hence,
when adopting the class view, we adapt it to the four forms,
as in the previous chapter.
3. The attributive view is supported by J. S. Mill.
He admits that it is natural to construe the subject in
extension and the predicate in intension (as in the
predicative interpretation) ; but he points out, what we
have already seen, that the extension of a term, the
class denoted by it, can be distinguished only through
the attributes. A class is not made by drawing
round a given number of individuals ;
a line
it consists of the
individuals which are found to have the attributes
signified by a given name. When we say
"All men
are mortal," we do not mean that this attribute is
possessed by a particular group of individuals that we
have in view ; we mean that the attribute is possessed
by any individual possessing certain other attributes,
those of "humanity." All this is quite sound. But
on this ground Mill holds that in interpreting the pro
position we may drop the reference to "things" (the
side of extension), and regard the proposition as giving
evidence only about the
"
"
concomitance of attributes :
"
Whatever has the attribute humanity has the attribute
mortality,"
or
"
Mortality always accompanies the
1 The philosophical aspects of Jevons s theory of Inference will be
further considered in ch. XI. 2.