A System of Logic: Ratiocinative and Inductive, 7th Edition, Vol. I — John Stuart Mill — John Shaqi
A System of Logic: Ratiocinative and Inductive, 7th Edition, Vol. I
John Stuart Mill · en
the Duke of Wellington, and then refused to stand to it in the
individual case. There is an inconsistency to be avoided between the
memorandum we make of the inferences which may be justly drawn in future
cases, and the inferences we actually draw in those cases when they
arise. With this view we interpret our own formula, precisely as a judge
interprets a law: in order that we may avoid drawing any inferences not
conformable to our former intention, as a judge avoids giving any
decision not conformable to the legislator's intention. The rules for
this interpretation are the rules of the syllogism: and its sole purpose
is to maintain consistency between the conclusions we draw in every
particular case, and the previous general directions for drawing them;
whether those general directions were framed by ourselves as the result
of induction, or were received by us from an authority competent to give
them.
§ 5. In the above observations it has, I think, been shown, that, though
there is always a process of reasoning or inference where a syllogism is
used, the syllogism is not a correct analysis of that process of
reasoning or inference; which is, on the contrary, (when not a mere
inference from testimony) an inference from particulars to particulars;
authorized by a previous inference from particulars to generals, and
substantially the same with it; of the nature, therefore, of Induction.
But while these conclusions appear to me undeniable, I must yet enter a
protest, as strong as that of Archbishop Whately himself, against the
doctrine that the syllogistic art is useless for the purposes of
reasoning. The reasoning lies in the act of generalization, not in
interpreting the record of that act; but the syllogistic form is an
indispensable collateral security for the correctness of the
generalization itself.
It has already been seen, that if we have a collection of particulars
sufficient for grounding an induction, we need not frame a general
proposition; we may reason at once from those particulars to other
particulars. But it is to be remarked withal, that whenever, from a set
of particular cases, we can legitimately draw any inference, we may
legitimately make our inference a general one. If, from observation and
experiment, we can conclude to one new case, so may we to an indefinite
number. If that which has held true in our past experience will
therefore hold in time to come, it will hold not merely in some
individual case, but in all cases of some given description. Every
induction, therefore, which suffices to prove one fact, proves an
indefinite multitude of facts: the experience which justifies a single
prediction must be such as will suffice to bear out a general theorem.
This theorem it is extremely important to ascertain and declare, in its
broadest form of generality; and thus to place before our minds, in its
full extent, the whole of what our evidence must prove if it proves
anything.