ul at the head of a railroad will
therefore make a good president for a college because that also is a
complex institution, or that because self-government has worked well in
a certain school it will probably work well in a college, or that
because a friend has been cured of sleeplessness by taking a walk just
before going to bed therefore everybody who sleeps badly can be cured in
the same way,--in all these cases you are reasoning by analogy. In each
case it will be noticed you would pass from a similarity which exists in
a single case or in a small number of cases to the conclusion. The
reasoning is sound, however, only in so far as the similarity bears on
the actual purpose in hand: in the first example, if the success of the
railroad president arises from the power of understanding men and of
philosophic insight into large problems, the reasoning will probably be
valid; in the last example, if applied to insomnia due to overwork, it
might be bad.

In practical affairs it is easy to find examples of reasoning from
analogy, especially in arguments of policy. The first trial of city
government by commission depended on such reasoning: when Galveston,
Texas, was devastated by a storm it was reasoned that in business
matters a small body of picked men with absolute powers are most
efficient in an emergency, and that since the reconstruction of the city
was essentially a matter of business, such a body would best meet the
emergency. So the extension of commission government in other states at
first followed reasoning by analogy: government by commission worked
well in Galveston; it would probably work well in Des Moines. In the
same way with the arguments for a parcels post: they proceed from the
analogy of the present postal service, which has been successful so far
as it goes, and from the success of the parcels post in almost all the
countries of Europe. If you were arguing that "Association" (or
"soccer") football should be made one of the major sports at your
college, you would reason from the analogy of its great popularity with
Englishmen all over the world that it would also probably be popular in
America.

When you use the argument from analogy, however, you must make sure that
the similarity between the two cases runs to the point you wish to
establish. In the following extract from an argument in favor of
commission government for all cities, the author explicitly limits his
reasoning from the analogy of Was