"You are more adapted to the profession of medicine; you can do more
good in this field," etc. If the friend should open the question, he
would be in the position of a man on the negative side of a debate. He
would state the issues negatively as his reasons. He would say: "I am
not so well adapted to the study of medicine; it offers less promise
of reward," etc.

Each of these would in turn depend upon other reasons, but every
proposition will depend for its acceptance on the proof of a few main
issues. Perhaps this point can be made clearer by an illustration.
Suppose we should take hold of one small rod which we see in the
framework of a large truss bridge and should say: "This bridge is
strong because this rod is here." Our statement would be only
partially true. The rod might be broken, and although the strength of
the bridge as a whole might be slightly weakened, it would not fall.
But suppose we should say: "This bridge really rests on these four
great steel beams which run down to the stone abutment. If I can see
that these four steel beams are secure, I can believe in the security
of the bridge." So a mechanical engineer shows us that certain rods
and bars of the framework hold up one beam, and how similar rods and
bars sustain a second, and that yet other rods and bars distribute the
weight that would press too heavily on a third, and so at last we are
convinced that the bridge is safe. It is not because we have been
shown that several of the bolts and braces are strong, but because we
have been shown that the four great beams, upon which it rests, are
reliable.

Thus it is with everything in which we believe. We do not believe that
taxes are just because the government must have money to pay the
president or to buy uniforms for the army officers. These things must