term is familiar to every one from murder
trials and detective stories. Webster's argument in the White Murder
Case, from which I print a short extract on page 157, is a famous
example of an argument on circumstantial evidence; and in fiction Sir
Conan Doyle has created for our delectation many notable and ingenious
cases of it. But reasoning from circumstantial evidence is far from
being confined to criminal cases and fiction; as Huxley points out (see
p. 241), it is also the basis of some of the broadest and most
illuminating generalizations of science; and the example below from
Macaulay is only one of innumerable cases of its use in history.

Reasoning from circumstantial evidence differs from reasoning from
analogy or generalization in that it rests on similarities reaching out
in a number of separate directions, all of which, however, converge on
the case in hand. This convergence is pointed out by Macaulay in the
following admirable little argument on the authorship of the _Junius
Letters_, which were a series of pseudonymous and malignant attacks on
the British government about 1770:

Was he [Francis] the author of the Letters of Junius? Our own firm
belief is that he was. The evidence is, we think, such as would support
a verdict in a civil, nay, in a criminal proceeding. The handwriting of
Junius is the very peculiar handwriting of Francis, slightly disguised.
As to the position, pursuits, and connections of Junius, the following
are the most important facts which can be considered as clearly proved:
first, that he was acquainted with the technical forms of the secretary
of state's office; secondly, that he was intimately acquainted with the
business of the war office; thirdly, that he, during the year 1770,
attended debates in the House of Lords, and look notes of speeches,
particularly of the speeches of Lord Chatham; fourthly, that he bitterly
resented the appointment of Mr. Chamier to the place of deputy
secretary-at-war; fifthly, that he was bound by some strong tie to the
first Lord Holland. Now, Francis passed some years in the secretary of
state's office. He was subsequently chief clerk of the war office. He
repeatedly mentioned that he had himself, in 1770, heard speeches of
Lord Chatham; and some of these speeches were actually printed from his
notes. He resigned his clerkship at the war office from resentment at
the appointment of Mr. Chamier. It was by Lord Holland that he was first
introduced int