beaten track may be attained; but that has not yet been done.

70. THE DOUBLE AFFILIATION OF PSYCHOLOGY.--In spite of what has been
said above, we must not forget that psychology is a _relatively_
independent science. One may be a useful psychologist without knowing
much about philosophy.

As in logic it is possible to write a text-book not greatly different
in spirit and method from text-books concerned with the sciences not
classed as philosophical, so it is possible to make a useful study of
mental phenomena without entering upon metaphysical analyses. In
science, as in common life, we can _use_ concepts without subjecting
them to careful analysis.

Thus, our common experience reveals that mind and body are connected.
We may, for a specific purpose, leave the _nature_ of this connection
vague, and may pay careful attention to the physiological conditions of
mental phenomena, studying in detail the senses and the nervous system.
We may, further, endeavor to render our knowledge of mental phenomena
more full and accurate by experimentation. In doing this we may be
compelled to make use of elaborate apparatus. Of such mechanical aids
to investigation our psychological laboratories are full.

It is to such work as this that we owe what is called the
"physiological" and the "experimental" psychology. One can carry on
such investigations without being a metaphysician. But one can
scarcely carry them on without having a good knowledge of certain
sciences not commonly supposed to be closely related to psychology at
all. Thus, one should be trained in chemistry and physics and
physiology, and should have a working knowledge of laboratory methods.