more refined varieties of touch. All of them are passive, and by this are
distinguished from the active faculty of speech: they receive impressions,
but do not produce them, except in so far as they are objects of sense
themselves.

Physiology speaks to us of the wonderful apparatus of nerves, muscles,
tissues, by which the senses are enabled to fulfil their functions. It
traces the connexion, though imperfectly, of the bodily organs with the
operations of the mind. Of these latter, it seems rather to know the
conditions than the causes. It can prove to us that without the brain we
cannot think, and that without the eye we cannot see: and yet there is far
more in thinking and seeing than is given by the brain and the eye. It
observes the 'concomitant variations' of body and mind. Psychology, on the
other hand, treats of the same subject regarded from another point of view.
It speaks of the relation of the senses to one another; it shows how they
meet the mind; it analyzes the transition from sense to thought. The one
describes their nature as apparent to the outward eye; by the other they
are regarded only as the instruments of the mind. It is in this latter
point of view that we propose to consider them.

The simplest sensation involves an unconscious or nascent operation of the
mind; it implies objects of sense, and objects of sense have differences of
form, number, colour. But the conception of an object without us, or the
power of discriminating numbers, forms, colours, is not given by the sense,
but by the mind. A mere sensation does not attain to distinctness: it is
a confused impression, sugkechumenon ti, as Plato says (Republic), until
number introduces light and order into the confusion. At what point
confusion becomes distinctness is a question of degree which cannot be
precisely determined. The distant object, the undefined notion, come out
into relief as we approach them or attend to them. Or we may assist the