tion to the ways and works of the lower animals suggests a
comparative anatomy and physiology of the mind; and the doctrine of
evolution presses for application as much in the one field as in the
other.

But there is more than a parallel, there is a close and intimate
connexion between psychology and physiology. No one doubts that, at any
rate, some mental states are dependent for their existence on the
performance of the functions of particular bodily organs. There is no
seeing without eyes, and no hearing without ears. If the origin of the
contents of the mind is truly a philosophical problem, then the
philosopher who attempts to deal with that problem, without acquainting
himself with the physiology of sensation, has no more intelligent
conception of his business than the physiologist, who thinks he can
discuss locomotion, without an acquaintance with the principles of
mechanics; or respiration, without some tincture of chemistry.

On whatever ground we term physiology, science, psychology is entitled
to the same appellation; and the method of investigation which
elucidates the true relations of the one set of phenomena will discover
those of the other. Hence, as philosophy is, in great measure, the
exponent of the logical consequences of certain data established by
psychology; and as psychology itself differs from physical science only
in the nature of its subject-matter, and not in its method of
investigation, it would seem to be an obvious conclusion, that
philosophers are likely to be successful in their inquiries, in
proportion as they are familiar with the application of scientific
method to less abstruse subjects; just as it seems to require no
elaborate demonstration, that an astronomer, who wishes to comprehend
the solar system, would do well to acquire a preliminary acquaintance
with the elements of physics. And it is accordant with this presumption,
that the men who have made the most important positive additions to
philosophy, such as Descartes, Spinoza, and Kant, not to mention more
recent examples, have been deeply imbued with the spirit of physical
science; and, in some cases, such as those of Descartes and Kant, have
been largely acquainted with its details. On the other hand, the founder
of Positivism no less admirably illustrates the connexion of scientific
incapacity with philosophical incompetence. In truth, the laboratory is
the fore-court of the temple of philosophy; and whoso has not offered