on is instituted. The two balls are like each other in form,
but unlike in material; whether is it in respect of their form or
their material that you propose to compare them? If one of them rolls
along a gently inclined plane, you may safely infer that the other,
when placed in the same position, will follow the same course; for
although different in other features they are similar in form. But
you cannot infer that because one floats when thrown into the water
the other will float too, for in respect to specific gravity there is
no similarity between them. Again, let two pieces of wood, cut from
the same tree, be brought together, the one a cube, the other a
sphere; you may safely conclude, if one swim in water that the other
will swim too, because though of diverse forms they are of the same
specific gravity; but you cannot conclude, if the one roll on an
inclined plane, that the other will roll also, because though of the
same specific gravity they are diverse forms. Two objects may be
compared for the purpose of inferential analogy, although in nine of
their qualities they are wholly dissimilar, if they resemble each
other in one, and that the quality with respect to which the
comparison is instituted. Again, although two objects be similar in
nine of their properties, and dissimilar only in one, no useful
analogy can be instituted between them if the object for which the
comparison is made save with respect to the one point in which they
are dissimilar. An acquaintance with such simple rudiments would go
far to correct blunders both in the construction and the exposition
of analogies.

In suggesting probabilities and throwing out lines of inquiry, analogy
is of unspeakable value in every branch of science; in sacred
apologetics its specific use is to destroy the force of objections which
may be plausibly urged against facts or doctrines otherwise established;
but it is as an instrument for explaining, illustrating, fixing, and
impressing moral and spiritual truth that we are mainly concerned with
it here.

God's word is as full of analogies as his works. The histories,
offerings, and prophecies of the Old Testament are figures of better
things which have been brought to light by the gospel. The lessons of
the Lord and his apostles teem with types. Almost every doctrine is
given in duplicate: the spirit is provided with a body; a body clothes
the spirit. Every fruit