vious reasons the simple Method of Difference is
inapplicable to tracing cause and effect in communities. Every new law
or repeal of an old law is the introduction of a new agency, but the
effects of it are intermixed with the effects of other agencies that
operate at the same time. Thus Professor Cairnes remarks, concerning
the introduction of a high Protective Tariff into the United States
in 1861, that before its results could appear in the trade and
manufacture of the States, there occurred (1) The great Civil War,
attended with enormous destruction of capital; (2) Consequent upon
this the creation of a huge national debt, and a great increase of
taxation; (3) The issue of an inconvertible paper currency, deranging
prices and wages; (4) The discovery of great mineral resources and
oil-springs; (5) A great extension of railway enterprise. Obviously in
such circumstances other methods than the Method of Difference must
be brought into play before there can be any satisfactory reasoning on
the facts observed. Still what investigators aim at is the isolation
of the results of single agencies.

[Footnote 1: Prof. Bain, who adopts Mill's Canon, silently
drops the words within brackets. They seem to be an
inadvertence. The "circumstance," in all the examples
that Mill gives, is an antecedent circumstance. Herschel's
statement, of which Mill's is an adaptation, runs as follows:
"If we can either find produced by nature, or produce
designedly for ourselves, two instances which agree exactly in
all but one particular and differ in that one, its influence
in producing the phenomenon, if it have any, must thereby be
rendered apparent".]

CHAPTER V.

METHODS OF OBSERVATION.--ELIMINATION.--SINGLE AGREEMENT.

I.--THE PRINCIPLE OF ELIMINATION.

The essence of what Mill calls the Method of Agreement is really the
elimination[1] of accidental, casual, or fortuitous antecedents. It
is a method employed when we are given an effect and set to work to
discover the cause. It is from the effect that we start and work back.
We make a preliminary analysis of the antecedents; call the roll, as
it were, of all circumstances present before the effect appeared. Then
we proceed to examine other instances of the same effect, and other
instances of the occurrence of the various antecedents, and bring to
bear the principle that any antecedent in the absence of which the
effect has appeared or on