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

THE VALIDITY OF THE SYLLOGISM. 209
have been put into this form. Fallacy may arise from
a faulty major or a faulty minor premise. In the
major premise the antecedent, or the consequent, may
be false in fact, or the asserted connection between
them may be false. In the minor premise where the
fallacy usually lies the antecedent of the major may
be affirmed or the consequent denied ; or the alter
natives may not be exclusive or not exhaustive. This
last is the most common source of hidden fallacy in
the dilemma, as Jevons has well shown.
"It is seldom possible to find instances where two
alternatives exhaust all the possible cases, unless indeed
one of them be the simple negative of the other in
accordance with the law of excluded middle. Thus if
we were to argue that if a pupil is fond of learning, he
needs no stimulus, and that if he dislikes learning, no
stimulus will be of any avail ; but as he is either fond
of learning or dislikes it, a stimulus is either needless or
of no avail, we evidently assume improperly the dis
junctive minor premise. Fondness and dislike are not
the only two possible alternatives, for there may be
some who are neither fond of learning nor dislike it,
and to these a stimulus in the shape of rewards may be
desirable. Almost anything can be proved if we are
allowed thus to pick out two of the possible alternatives
which are in our favour, and argue from these alone."
The most famous illustration of these observations is
the ancient fallacy known as Ignava Ratio, the "lazy
argument :
"If it be fated that you recover from your
present disease, you will recover, whether you
call in a
doctor or not ; again, if it be fated that you do not recover
from your present disease, you will not recover, whether
you
call in a doctor or not : but one or other of these con
tradictories is fated, and therefore it can be of no service to
call in a doctor." Here the minor premise assumes that
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