A System of Logic, Ratiocinative and Inductive (Vol. 1 of 2) — John Stuart Mill — John Shaqi
A System of Logic, Ratiocinative and Inductive (Vol. 1 of 2)
John Stuart Mill · en
And since a large portion of our knowledge is thus acquired, logicians
have persisted in representing the syllogism as a process of inference or
proof; although none of them has cleared up the difficulty which arises
from the inconsistency between that assertion, and the principle, that if
there be anything in the conclusion which was not already asserted in the
premisses, the argument is vicious. For it is impossible to attach any
serious scientific value to such a mere salvo, as the distinction drawn
between being involved _by implication_ in the premisses, and being
directly asserted in them. When Archbishop Whately, for example, says,(31)
that the object of reasoning is “merely to expand and unfold the
assertions wrapt up, as it were, and implied in those with which we set
out, and to bring a person to perceive and acknowledge the full force of
that which he has admitted,” he does not, I think, meet the real
difficulty requiring to be explained, namely, how it happens that a
science, like geometry, _can_ be all “wrapt up” in a few definitions and
axioms. Nor does this defence of the syllogism differ much from what its
assailants urge against it as an accusation, when they charge it with
being of no use except to those who seek to press the consequences of an
admission into which a person has been entrapped without having considered
and understood its full force. When you admitted the major premiss, you
asserted the conclusion; but, says Archbishop Whately, you asserted it by
implication merely: this, however, can here only mean that you asserted it
unconsciously; that you did not know you were asserting it; but, if so,
the difficulty revives in this shape—Ought you not to have known? Were you
warranted in asserting the general proposition without having satisfied
yourself of the truth of everything which it fairly includes? And if not,
what then is the syllogistic art but a contrivance for catching you in a
trap, and holding you fast in it?(32)
§ 3. From this difficulty there appears to be but one issue. The
proposition that the Duke of Wellington is mortal, is evidently an
inference; it is got at as a conclusion from something else; but do we, in
reality, conclude it from the proposition, All men are mortal? I answer,
no.
The error committed is, I conceive, that of overlooking the distinction
between the two parts of the process of philosophizing, the inferring
part, and the registering part; and ascribing to the latter the functions
of the former. The mistake is that of referring a person to his own notes
for the origin of his knowledge. If a person is asked a question, and is
at the moment unable to answer it, he may refresh his memory by turning to
a memorandum which he carries about with him. But if he were asked, how
the fact came to his knowledge, he would scarcely answer, because it was
set down in his note-book: unless the book was written, like the Koran,
with a quill from the wing of the angel Gabriel.