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

OR SCIENTIFIC METHOD. 29!
clitions. It does not warrant the empirical law "if A, then
a whatever the circumstances be."
t may The conclusion
which it actually does warrant, that
"
the cause A in the cir
cumstances bed has the effect a" if the experiment is careful
enough, may be made the ground of a universal law by the
principle of the "
Uniformity of Causation : the cause A under
the same circumstances will always have the same effect."
For instance, we may know from observation and experi
ment that
"
quinine affects beneficially the nervous system
and the health of the body generally, while strychnine has a
terrible effect of the opposite nature." But we can give no
other reason for the truth of such generalisations, (d) The
Double Methods of Agreement and Difference, as we have
shown, serve to make the resulting generalisations more
trustworthy/.*., we are able to affirm with greater confidence
that A, and A only, is always the cause of a; but still they
do not show why it is, they do not give us more than
empirical laws.
is the cause of a, we pass to
A When we ask
"
"
how
Explanation. We have seen that the distinction between
these is not an absolute one ; they are two stages of one
process. That there is a real distinction is seen in the
fact that some sciences have not got beyond the stage of
Observation,
the
"
empirical stage," as it may
be called.
10. It was remarked in passing that the methods
which we have already explained cannot get to work
without the aid of a preliminary guess, supposition, or
suggestion of a possible cause for the phenomenon
under investigation.
First, then, we must have an assumption as to the
locality, and possibly the nature, of the cause ; and the
Methods of Observation and Experiment exist in order to
test such suggestions. Every research by which we seek
to discover truth must be guided by some conjecture :
whether it be a theoretical suggestion of a cause, or the
practical suggestion of something to be accomplished.