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
Induction, as above defined, is a process of inference; it proceeds from
the known to the unknown; and any operation involving no inference, any
process in which what seems the conclusion is no wider than the premisses
from which it is drawn, does not fall within the meaning of the term. Yet
in the common books of Logic we find this laid down as the most perfect,
indeed the only quite perfect, form of induction. In those books, every
process which sets out from a less general and terminates in a more
general expression,—which admits of being stated in the form, “This and
that A are B, therefore every A is B,”—is called an induction, whether
anything be really concluded or not; and the induction is asserted to be
not perfect, unless every single individual of the class A is included in
the antecedent, or premiss: that is, unless what we affirm of the class
has already been ascertained to be true of every individual in it, so that
the nominal conclusion is not really a conclusion, but a mere reassertion
of the premisses. If we were to say, All the planets shine by the sun’s
light, from observation of each separate planet, or All the Apostles were
Jews, because this is true of Peter, Paul, John, and every other
apostle,—these, and such as these, would, in the phraseology in question,
be called perfect, and the only perfect, Inductions. This, however, is a
totally different kind of induction from ours; it is no inference from
facts known to facts unknown, but a mere short-hand registration of facts
known. The two simulated arguments which we have quoted, are not
generalizations; the propositions purporting to be conclusions from them,
are not really general propositions. A general proposition is one in which
the predicate is affirmed or denied of an unlimited number of individuals;
namely, all, whether few or many, existing or capable of existing, which
possess the properties connoted by the subject of the proposition. “All
men are mortal” does not mean all now living, but all men past, present,
and to come. When the signification of the term is limited so as to render
it a name not for any and every individual falling under a certain general
description, but only for each of a number of individuals designated as
such, and as it were counted off individually, the proposition, though it
may be general in its language, is no general proposition, but merely that
number of singular propositions, written in an abridged character. The
operation may be very useful, as most forms of abridged notation are; but
it is no part of the investigation of truth, though often bearing an
important part in the preparation of the materials for that investigation.