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

302
THE THEORY OF INDUCTION
or compare other cases, according to the canons of
inductive observation. But it suggests that both cases
may be instances of a general law under which they
fall. It prompts us to extend our knowledge of the
first case and found on it a law of connection which
includes the second.
Thus, suppose we have a suggested connection, S is P. It
may be suggested, in the way we have described, by the
Method of Agreement (otherwise, by an Enthymeme in
fig. iii.) ; but this particular kind of suggestion need not
necessarily precede. If we can find some fact M to be an
important circumstance in both S and P, we may justify the
original suggestion by an analogical inference, thus :
P is M,
Sis M;
. . S and P are probably causally connected through M.
This is of course an Aristotelian Enthymeme in fig. ii. The
"
suggested explanation is, to investigate the connection of
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M and P further, in order to determine whether M is the
cause of P. If this relation can be established, then we may
"
"
explain P, bringing both S and P under the universal M.
Stated syllogistically, this becomes a valid syllogism in fig. i.
(a syllogism
"
of cause :
")
M is P,
Sis M;
. . S is P.
For concrete examples, the student may refer to ch. VIII.
3. In 3 (a), Ex. 3 is a suggestion based on Agreement ;
in 3 (<), Ex. 3 is an analogical justification of the same
suggestion ; in 3 (c), Ex. 3 is an explanation of the sug
gested connection by a law of real causation. Similarly,
3 (a), Ex. 4, is a suggestion based on Agreement ; and
3 (b\ Ex. 4, is an analogical justification of it.
It thus appears that an analogical inference is a stage
or step in the complete inductive process. If the
analogical inference to the new particular case is justifi-