An introductory text-book of logic - Mellone, Sydney - Rare Books at ...

THE GENERAL NATURE OF INDUCTION. 243
"
tion is true of the one, therefore it is true of the other
have all
(Mill, Logic, III. xx. 2). The inference may
degrees of value, from being worse than worthless (when
the resemblance lies in merely accidental qualities), to
being a ground for a practically certain conclusion. Its
worth depends on the importance of the points of re
semblance on which it is based.
On what does the
"
"
importance of the points of
resemblance depend? Not on the mere number of
resemblances, as Mill said,
resemblance compared first with the amount of ascer
"the extent of ascertained
tained difference, and next with the extent of the un
explored region
"
"
unexplored region
of unascertained differences." The
here referred to cannot be used
as a standard of comparison, simply because it is "un
And the unknown range of points of differ
explored."
ence between the two cases makes it impossible to take
the mere ratio of known resemblances to known differ
ences as a valid ground for an inference, as Mill
maintains (Logic, III. xx. 3). Two cases may resemble
one another in a very large number of unimportant
respects, affording not the least ground for inferring a
resemblance in any other quality. For instance, two
boys may resemble one another in height, features,
strength, and other physical gifts, may be of the same
age, born in the same town, educated in the same way,
come from families of similar social position and cultiva
tion ; yet could we infer that because one of them has
native mental abilities of a high order, the other will have
the same ? If the number of points of resemblance were
the essential thing, the argument ought to possess some
force ; but it is clearly worthless. The reason is that
none of the points of resemblance are fundamental.
Hence, as Mr Bosanquet says, in Analogy we must