ful; or, if
we see some one come to grief, we try to see how it happened, so as to
avoid his mistake and so the bad consequences of that mistake. We plan
to perform M so as to secure P, or to avoid M in the hope of avoiding
P.

Sometimes, not so rarely, we have both premises handed out to us and
have only to draw the conclusion. More often, we hear a person drawing
a conclusion from only one expressed premise, and try to make out what
the missing premise can be. Sometimes this is easy, as when one says,
"I like him because he is always cheerful", from which you see that
the person speaking must like cheerful persons. But if you hear it
said that such a one "cannot be a real thinker, he is so positive in
his opinions" or that another "is unfeeling and unsympathetic from
lack of a touch of cruelty in his nature", you may have to explore
about considerably before finding acceptable major premises from which
such conclusions can be deduced.

Finally, in asking what are the _qualifications of a good reasoner_ we
can help ourselves once more by reference to the syllogistic map. To
reason successfully on a given topic, you need good major premises,
good minor premises, and valid conclusions therefrom.

(a) A good stock of major premises is necessary, a good stock of rules
and principles acquired in previous experience. Without some knowledge
of a subject, you have only vague generalities to draw upon, and your
reasoning process will be slow and probably lead only to indefinite
conclusions. {479} Experience, knowledge, memory are important in
reasoning, though they do not by any means guarantee success.

(b) The "detective instinct" for finding the right clues, and
rejecting false leads, amounts to the same as sagacity in picking out
the useful minor premises. In problem solution, you have to find both
of your premises, and often the minor premise is the first to be found
and in turn recalls the appropriate major premise. Finding the minor
premise is a matter of observation, and if you fail to observe the
significant fact about the problem, the really useful major premise
may lie dormant, known and retained but not recalled, while false
clues suggest inapplicable major premises and give birth to plenty of
reasoning but all to no purpose. Some persons with abundant knowledge
are ineffective reasoners from lack of a sense for probability. The
efficient reasoner must be a good guesser.

(c) The reasoner needs a clear and ste