body, and so to reduce mental operations
to the level of bodily ones, or to confound one with the other.

g. That the progress of Physiology may throw a new light on Psychology
is a dream in which scientific men are always tempted to indulge. But
however certain we may be of the connexion between mind and body, the
explanation of the one by the other is a hidden place of nature which
has hitherto been investigated with little or no success.

h. The impossibility of distinguishing between mind and body. Neither
in thought nor in experience can we separate them. They seem to act
together; yet we feel that we are sometimes under the dominion of the
one, sometimes of the other, and sometimes, both in the common use of
language and in fact, they transform themselves, the one into the good
principle, the other into the evil principle; and then again the 'I'
comes in and mediates between them. It is also difficult to distinguish
outward facts from the ideas of them in the mind, or to separate the
external stimulus to a sensation from the activity of the organ, or this
from the invisible agencies by which it reaches the mind, or any process
of sense from its mental antecedent, or any mental energy from its
nervous expression.

i. The fact that mental divisions tend to run into one another, and that
in speaking of the mind we cannot always distinguish differences of kind
from differences of degree; nor have we any measure of the strength and
intensity of our ideas or feelings.

j. Although heredity has been always known to the ancients as well as
ourselves to exercise a considerable influence on human character, yet
we are unable to calculate what proportion this birth-influence bears to
nurture and education. But this is the real question. We cannot pursue
the mind into embryology: we can only trace how, after birth, it begins
to grow. But how much is due to the soil, how much to the original
latent seed, it is impossible to distinguish. And because we are certain
that heredity exercises a considerable, but undefined influence, we must
not increase the wonder by exaggerating it.

k. The love of system is always tending to prevail over the historical
investigation of the mind, which is our chief means of knowing it. It
equally tends to hinder the other great source of our knowledge of the
mind, the observation of its workings and processes which we can make
for ourselves.

l. The mind, when studied through the individual,