to certain data merely common sense, the wisdom
of experience, analyzed, formulated, and codified_.

_It has taken its place, alongside physics and
chemistry, as the ally and employee of trade and
industry_.

The time has come when a man's knowledge
of his business, if the larger success is to be
won, must embrace an understanding of the
laws which govern the thinking and acting of
the men who make and sell his products as well
as those others who buy and consume them.

The achievements of the human mind and
the human body seem to many to be out of
the range of possible improvement through
application of any science which deals with
these human activities. Muscular strength
and mental efficiency seem to be fixed quantities
not subject to increase or improvement.

_The contention here supported, however, is
that human efficiency is a variable quantity
which increases and decreases according to law.
By the application of known physical laws the
telephone and the telegraph have supplanted the
messenger boy. By the laws of psychology
applied to business equally astounding improvements
are being and will be secured_.