MACAULAY: _Copyright_, 1841

Analogy. In argument by analogy the speaker attempts to prove that
because certain things are known to be true in something that can be
observed they are likely to be true in something else which in so far
as it can be observed is quite like the first. We continually argue by
analogy in daily life. Lincoln was really using analogy when he
replied to the urging to change his army leaders during the Civil War,
that he didn't think it wise to "swap horses while crossing a
stream." Scientists use this method to draw conclusions when it is
impossible to secure from actual observation or experiment a certain
last step in the reasoning. The planet Mars and the earth are similar
in practically all observable matters; they are about the same
distance from the sun, they have the same surface conditions. The
earth has living creatures upon it. Hence--so goes the reasoning of
analogy--Mars is probably inhabited. Reasoning by analogy is used to
prove that universal suffrage is good for the United States because it
has been good for one particular state. A student may argue by analogy
that the elective system should be introduced into all high schools,
because it has been followed in colleges. It may be asserted that a
leading bank president will make a good university president, because
he has managed one complex institution. The essence of all good
reasoning by analogy is that the two things considered must be so
nearly alike in all that is known that the presumption of belief is
that they must also be alike in the one point the arguer is trying to
establish. This is the test he must apply to his own analogy
arguments.

Our community frowns with indignation upon the profaneness
of the duel, having its rise in this irrational point of
honor. Are you aware that you indulge the same sentiment on
a gigantic scale, when you recognize this very point of
honor as a proper apology for war? We have already seen that
justice is in no respect promoted by war. Is true honor
promoted where justice is not?

CHARLES SUMNER: _The True Grandeur of Nations_,
1845

Residues. The method of residues is frequently employed when the
speaker is supporting a policy to be carried out, a measure to be
adopted, a change to be instituted, or a law to be passed. Granting
the assumption that something must be done he considers all the
various methods which may be employed, disposes o