psychology has come into her own as a
recognized science of the mind, just as biology, histology, chemistry,
pathology, and medicine are recognized sciences governing the body. As
these are concerned with the "how" and "why" of life, and of the body
reactions, so psychology is concerned with the "how" and "why" of
conduct and of thinking. For as truly as every infectious disease is
caused by a definite germ, just as truly has every action of man its
adequate explanation, and every thought its definite origin. As we would
know the laws of the sciences governing man's physical well-being that
we might have body health, so we would know the laws of the mind and of
its response to its world in order to attain and hold fast to mind
health. Experience with patients soon proves to us nurses that the weal
and woe of the one vitally affects the other.

"Psychology is the science of mental life, both of its phenomena and
their conditions."

So William James took up the burden of proof some thirty years ago, and
assured a doubting world of men and women that there were laws in the
realm of mind as certain and dependable as those applying to the world
of matter--men and women who were not at all sure they had any right to
get near enough the center of things to see the wheels go round. But
today thousands of people are trying to find out something of the way
the mind is conceived, and to understand its workings. And many of us
have in our impatient, hasty investigation, self-analytically taken our
mental machines all to pieces and are trying effortfully to put them
together again. Some of us have made a pretty bad mess of it, for we
tore out the screws and pulled apart the adjustments so hastily and
carelessly that we cannot now find how they fit. And millions of other
machines are working wrong because the engineers do not know how to keep
them in order, put them in repair, or even what levers operate them. So
books must be written--books of directions.

If you can glibly recite the definition above, know and explain the
meaning of "mental life," describe "its phenomena and their conditions,"
illustrating from real life; if you can do this, and prove that
psychology is a science, _i. e._, an organized system of knowledge on
the workings of the mind--not mere speculation or plausible theory--then
you are a psychologist, and can make your own definitions. Indeed, the
test of the value of a course such as this should be your abili