Thus we see that no line can be drawn between the powers of sense and of
reflection--they pass imperceptibly into one another. We may indeed
distinguish between the seeing and the closed eye--between the sensation
and the recollection of it. But this distinction carries us a very little
way, for recollection is present in sight as well as sight in recollection.
There is no impression of sense which does not simultaneously recall
differences of form, number, colour, and the like. Neither is such a
distinction applicable at all to our internal bodily sensations, which give
no sign of themselves when unaccompanied with pain, and even when we are
most conscious of them, have often no assignable place in the human frame.
Who can divide the nerves or great nervous centres from the mind which uses
them? Who can separate the pains and pleasures of the mind from the pains
and pleasures of the body? The words 'inward and outward,' 'active and
passive,' 'mind and body,' are best conceived by us as differences of
degree passing into differences of kind, and at one time and under one
aspect acting in harmony and then again opposed. They introduce a system
and order into the knowledge of our being; and yet, like many other general
terms, are often in advance of our actual analysis or observation.

According to some writers the inward sense is only the fading away or
imperfect realization of the outward. But this leaves out of sight one
half of the phenomenon. For the mind is not only withdrawn from the world
of sense but introduced to a higher world of thought and reflection, in
which, like the outward sense, she is trained and educated. By use the
outward sense becomes keener and more intense, especially when confined
within narrow limits. The savage with little or no thought has a quicker
discernment of the track than the civilised man; in like manner the dog,
having the help of scent as well as of sight, is superior to the savage.
By use again the inward thought becomes more defined and distinct; what was
at first an effort is made easy by the natural instrumentality of language,