ent. All the cases must be known for a perfect induction; there
is no unknown to argue to. This, then, is only a short statement of
many individual truths, and has but little of value. Induction that is
imperfect is more valuable; for with many cases the probability
becomes so strong that it is a practical certainty. It is the method
of science.

More valuable for literature is another division of arguments into
arguments from cause, arguments from sign, and arguments from example.

Arguments from Cause.

Arguments from cause include those propositions which, if they were
granted, would account for the fact or proposition maintained. The
decisive test is to suppose the proposition to be true; then, if it
will account for the condition, it is an argument from cause. A child
holds its finger in a flame; therefore its finger is burned. If the
first proposition be supposed to be true, it will account for a burned
finger. It is an argument from cause, and it is conclusive. Again, if
a man severs his carotid artery, he will die. If the first proposition
be supposed to be true, it will account for the man's subsequent
death. Now, supposing a man takes strychnine, he will die. This is not
quite so sure. If a stomach-pump were used or an antidote given, he
might not die. The cause has been hindered in its action, or another
cause has intervened to counterbalance the first. If, then, a cause be
adequate to produce the effect, and if it act unhindered or
unmodified, the effect will certainly follow the active cause. An
argument that uses as a premise such a cause may predicate its effect
as a conclusion with absolute certainty. Such an argument is
conclusive.

The argument from cause is used more frequently to establish a
probability than to prove a fact or proposition. However strong the
proofs of a statement may be, men hesitate to accept either the
statement or the proofs if the proposition is not plausible, or, as
people say, if "they do not understand it," or if "it is not
reasonable." If a murder be done and circumstances all point to your
friend, you do not believe your friend to be the criminal until some
fact is produced sufficient to cause your friend to commit the
crime,--until some motive is established. If it be shown that the
friend hated the murdered man and would be benefited by his death, a
motive is established,--the proposition is made plausible. A man could
"understand how he came to do it." The hatred a