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

THE VALIDITY OF THE SYLLOGISM. 223
have their angles equal to two right ?" angles If the reply
"
I do know the it," objector produces a triangle whose
is,
existence was unknown to the respondent, and asserts that
as its existence was unknown to him, the equality
of its
angles to two right angles must have been also unknown ;
hence he did not really know the general proposition which
he had asserted. Now there were some who considered
the right reply to be, "All the triangles that we know have
their angles equal to two right angles," not simply "all
triangles." This, says Aristotle, is not the correct reply.
"
They do know what they have demonstration of, and
the general proposition which they accepted was a demon
strated principle ; it concerned not only the triangles which
they were aware of as such, but every triangle without
qualification. There is no reason, however, in my opinion
why a man should not know in a sense what he is learning
while in another sense he is ignorant of it. The real
absurdity would not be this ; but that he should know
what he is learning in the same sense as when he has
learnt it." (An. Post., i.
i.)
In the words which are italicised in this passage, Aristotle
consciously and definitely accepts the view that the true
universal judgment is a generic judgment (ch. XI. 4). It
asserts a connection of attributes which depends only on
the attributes themselves ; they are such that one must
follow from the other e.g., the equality of the interior
angles to two right angles
of the triangle. When the
from the Euclidean
major premise
definition
of a syllogism
is a generic universal, it includes any particular instance
"
in a sense," as Aristotle says, in the sense that the law
is potentially applicable to any instance.
"
In another
sense" it does not include the particular case i.e., not
until the latter is explicitly stated, in the minor premise, as
an instance of the general law.