ons it is because we know of exceptions (we have seen kettles not
made of iron), or because we do not know of instances (we may never have
seen a raccoon, and so not know what he does in the daytime). The greater
the number of cases which have occurred without presenting an exception,
the stronger our belief in the truth of the proposition (we expect the sun
to rise because it has never failed).

The process by which, from many individual cases, we establish the truth
of a proposition is called +inductive reasoning+.

+175. Establishing a General Theory.+--A general theory is established by
showing that for all known particular cases it will offer an acceptable
explanation. By investigation or experiment we note that a certain fact is
true in one particular instance, and, after a large number of individual
cases have been noted, and the same fact found to be true in each, we
assume that such is true of all like cases, and a general law is
established. This is the natural scientific method and is constantly being
made use of in pursuing scientific studies. By experiment, it was found
that one particular kind of acid turned blue litmus red. This, of course,
was not sufficient proof to establish a general law, but when, upon
further investigation, it was found to be true of all known acids,
scientists felt justified in stating the general law that acids turn blue
litmus red.

In establishing a new theory in science it is necessary to bring forward
many facts which seem to establish it, and the argument will consist in
pointing out these facts. Frequently the general principle is assumed to
be true, and the argument then consists in showing that it will apply to
and account for all the facts of a given kind. Theories which have been
for a time believed have, as the world progressed in learning, been found
unable to account for all of a given class of conditions. They have been
replaced, therefore, by other theories, just as the Copernican theory of
astronomy has displaced the Ptolemaic theory.

Our belief may be based upon the absence of facts proving the contrary as
well as upon the presence of facts proving the proposition. If A has never
told an untruth, that fact is an argument in favor of his truthfulness on
the present occasion. A man who has never been dishonest may point to this
as an argument in favor of placing him in a position of trust. Often the
strongest evidence that we can offer in favor of a proposition