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

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THE THEORY OF INDUCTION
chief object and the great difficulty of the Methods of
Observation and Experiment is to isolate a cause that
is, prove that A produces a by getting A to act as far
as possible in isolation ( 4 and 7). The chief object
and the great difficulty of scientific Explanation is to
break down this isolation by connecting the action of
A with the action of other causes.
When a law is ascertained by the Methods of Observa
tion and Experiment, and we do not know why the law
should hold, it is said to be an empirical law (e/jLTreipia,
experience or trial). Hence an empirical law is one
which we do not yet see how to connect with previous
knowledge.
Mill says that
"
scientific inquirers give the name of em
pirical laws to uniformities which observation or experiment
has shown to exist, but on which they hesitate to rely in
cases varying much from those which have been actually
observed, for want of seeing any reason why such a law
should exist" (Logic, Bk. III. xvi. i). To this we must add
that the degree of reliability of such a law varies according
to the method by which it was established, "
(a) Horned
"
animals are ruminants
: this is an instance of Agreement
which is scarcely more than a simple enumeration, and
affords no presumption of causal connection. Hence there
is a certain doubt in extending it to any new case of a
"horned animal." () "Where dew is formed, the dewed
surface is colder than the air" : surrounding this connection
has been ascertained in many instances, varying from one
another in other respects. The resulting empirical law may
therefore be extended to new cases "differing from those
previously observed," with greater confidence than in the
former case. The same remark applies to many instances of
the Method of Single Agreement, such as those given in 3.
(c) The Method of Single Difference gives us reliable know
ledge of the action of a cause under the given conditions of
the experiment ; but as we have seen, it does not give us
knowledge of the action of the same cause under new con-