politicians would not be able to make, as, for instance, those
regarding the influences of the business cycle in politics.

The essence of scientific method is to hold constant all factors
except the one whose influence is to be measured. This is what
the chemist does in his laboratory and what the psychologist
does with his guinea pigs. The author does the same thing with
partial correlation. Social science, unlike mathematics, is not
an arm-chair science. That the author knows his data, as well
as his method, is evident from his apparent wide acquaintance
with Chicago political leaders, big and little, with ward bound-
aries, locales of operations, and services of precinct captains and
ward bosses. This orientation with the realities of everyday
politics makes his book more readable than others dealing with
less concrete material.

The modern scientific methods of trend lines, variance,
multiple correlation, and factorial analysis have in recent years
made much of economics, sociology, and psychology exact
science. But for some reason their advance in political science
has been slow. Perhaps Dr. Gosnell's work is a signal for a
general forward movement which is surely inevitable some time
in the distinguished field of political science.

WILLIAM FIELDING OGBURN

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