cular. The planet Mars, for
example, resembles the earth in shape, motion, atmosphere, change of
seasons, and relation to the sun; and from the resemblance in these
known particulars some persons have inferred that, like the earth, it is
also inhabited.

Analogical reasoning has a prominent place in our mental operations.
Analogy lies at the basis of simile, metaphor, and personification,
which are often used in argumentation. We frequently use analogical
processes in the practical affairs of life, inferring, for example, that
there will be rain to-day because the temperature, appearance of the
clouds, and the condition of the atmosphere resemble those of a rainy
day last week.

But it is to be observed that the arguments from analogy give us at the
best only probable truth. The degree of probability depends upon the
nature and number of the resemblances upon which the conclusion is
based. There must be no point of dissimilarity that would disprove the
conclusion inferred.

(3) We may establish a conclusion by an array of facts. This is called
inductive reasoning. We observe, for example, that A, B, C, and all
other men of the past, so far as our knowledge goes, have died; and in
view of these individual cases we draw the comprehensive conclusion that
all men are mortal.

But this mode of reasoning, common and indispensable as it is, needs to
be employed with caution. There is always danger of inferring more than
the facts warrant. When the inference is based on an inadequate
induction of facts, the process is called "jumping at a conclusion,"--a
mistake that is frequently made. Even large inductions are not always
safe. We might conclude, for instance, that, because the bulldog, hound,
mastiff, setter, spaniel, terrier, and other species we have known, are
accustomed to bark, therefore all dogs bark. Yet this apparently
well-founded conclusion is erroneous, for there is a non-barking species
in Greenland.

(4) Again, we may establish a truth by showing that it comes within an
established and recognized principle. This process is known as deductive
reasoning. The principle on which deductive reasoning depends is the
self-evident truth that "whatever is true of the whole is true of the
parts." Starting from the general truth that all men are mortal, we may
conclude that A, B, and C are mortal.

The general truth that supplies the basis of deductive reasoning may be
taken from various sources. Sometimes the truth