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

OR SCIENTIFIC METHOD. 269
the Method of Concomitant Variations, and the Method
of Residues. For these methods Mill makes high
claims, which in other parts of his work he is obliged
to retract. We shall see that they are not independent
and when
of one another, and not equally fundamental ;
we thus understand their relations to each other, and
the work that they will do, we shall see that they are
sound in principle, and are actually employed in
scientific investigations. In fact, Mill s account of
them is based on Herschel s description of the methods
of Induction in the Discourse to which we have already -
referred.
Mill explains that in all the methods there are only
two principles involved.
" The simplest and most
obvious modes of singling out from among the circum
stances which precede or follow a phenomenon, those
with which it is really connected by an invariable law,
are two in number. One is by comparing together
different instances in which the phenomenon occurs.
The other is by comparing together instances in which
the phenomenon does occur with instances (in other
in which it does not. These two
respects similar)
methods may be respectively denominated the Method
of Agreement and the Method of Difference" (Logic,
III. viii.
i). These are the two primary methods ; the
"
Joint Method," as described by Mill, is a double
application of the method of
"
"
Agreement ; the
method of
"
"
Concomitant Variations is a quantitative
application of either of the two primary methods ; and
the method of "Residues," as Mill conceives it, is a
variety
of the method of
"
Difference."
3. Mill states the Method of Agreement better
named the method of Single Agreement as follows :
"
If two or more instances of the phenomenon under