When he deals with the remaining or invalid modes of the First
figure, his manner of showing their invalidity is different, and in
itself somewhat curious. "If (he says) the major term is affirmed of
all the middle, while the middle is denied of all the minor, no
necessary consequence follows from such being the fact, nor will
there be any syllogism of the two extremes; for it is equally
possible, either that the major term may be affirmed of all the
minor, or that it may be denied of all the minor; so that no
conclusion, either universal or particular, is necessary in all
cases."[27] Examples of such double possibility are then exhibited:
first, of three terms arranged in two propositions (A and E), in
which, from the terms specially chosen, the major happens to be truly
affirmable of all the minor; so that the third proposition is an
universal Affirmative:--
Major and }
} Animal is predicable of every Man;
Middle. }
Middle and }
} Man is not predicable of any Horse;
Minor }
Major and }
} Animal is predicable of every Horse.
Minor }
Next, a second example is set out with new terms, in which the major
happens not to be truly predicable of any of the minor; thus
exhibiting as third proposition an universal Negative:--
Major and }
} Animal is predicable of every Man;
Middle. }
Middle and }
} Man is not predicable of any Stone;
Minor }
Major and }
} Animal is not predicable of any Stone.
Minor }
Here we see that the full exposition of a syllogism is indicated with
real terms common and familiar to every one; alphabetical symbols
would not have sufficed, for the learner must himself recognize the
one conclusion as true, the other as false. Hence we are taught that,
after two premisses thus conditioned, if we venture to join together
the major and minor so as to form a pretended conclusion, we may in
some cases obtain a true proposition universally Affirmative, in
other cases a true proposition universally Negative. Therefore
(Aristotle argues) there is no one necessary conclusion, the same in
all cases, derivable from such premisses; in other words, this mode
of syllogism is invalid and proves nothing. He applies the like
reasoning to all the other invalid modes of the first Figure; setting
them aside in the same way, and producing examples wherein double and
opposite conclusions (improperly so called), both true, are obtained
in different cases from the like arrangement of premisses.
[Footnote 27: Analyt. Prior. I. iv. p. 26, a. 2, seq.]
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