A System of Logic: Ratiocinative and Inductive, 7th Edition, Vol. II
John Stuart Mill · en
§ 1. The word Analogy, as the name of a mode of reasoning, is generally
taken for some kind of argument supposed to be of an inductive nature,
but not amounting to a complete induction. There is no word, however,
which is used more loosely, or in a greater variety of senses, than
Analogy. It sometimes stands for arguments which may be examples of the
most rigorous Induction. Archbishop Whately, for instance, following
Ferguson and other writers, defines Analogy conformably to its primitive
acceptation, that which was given to it by mathematicians, Resemblance
of Relations. In this sense, when a country which has sent out colonies
is termed the mother country, the expression is analogical, signifying
that the colonies of a country stand in the same _relation_ to her in
which children stand to their parents. And if any inference be drawn
from this resemblance of relations, as, for instance, that obedience or
affection is due from colonies to the mother country, this is called
reasoning by analogy. Or if it be argued that a nation is most
beneficially governed by an assembly elected by the people, from the
admitted fact that other associations for a common purpose, such as
joint-stock companies, are best managed by a committee chosen by the
parties interested; this, too, is an argument from analogy in the
preceding sense, because its foundation is, not that a nation is like a
joint stock company, or Parliament like a board of directors, but that
Parliament stands in the same _relation_ to the nation in which a board
of directors stands to a joint stock company. Now, in an argument of
this nature, there is no inherent inferiority of conclusiveness. Like
other arguments from resemblance, it may amount to nothing, or it may be
a perfect and conclusive induction. The circumstance in which the two
cases resemble, may be capable of being shown to be the _material_
circumstance; to be that on which all the consequences, necessary to be
taken into account in the particular discussion, depend. In the example
last given, the resemblance is one of relation; the _fundamentum
relationis_ being the management by a few persons, of affairs in which a
much greater number are interested along with them. Now, some may
contend that this circumstance which is common to the two cases, and the
various consequences which follow from it, have the chief share in
determining all the effects which make up what we term good or bad
administration. If they can establish this, their argument has the force
of a rigorous induction; if they cannot, they are said to have failed in
proving the analogy between the two cases; a mode of speech which
implies that when the analogy can be proved, the argument founded on it
cannot be resisted.