A System of Logic: Ratiocinative and Inductive, 7th Edition, Vol. I
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 premises
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 not to be perfect, unless every single individual
of the class A is included in the antecedent, or premise: 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 premises. 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 not an 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.