sense, it is necessary to perceive the form of the concrete sensation
which gave rise to it; for although the representation is indefinite or
generic, that is, not obvious to the external senses, yet it is not
physiologically distinct from the sensation of the quality described;
the perception of that quality is present by the aid of memory to the
inner consciousness.

It is therefore evident that the physiological elements of consciousness
are actually contained in so-called abstract ideas, although it is
sometimes asserted that they are purely spiritual and intellectual acts,
remote from every physiological process of fact and sense. An actual
physiological fact (colour in this instance) corresponds to the idea in
the nervous centres, and reproduces the sensation due to the perception
of special objects, whose physical quality of whiteness we have
perceived, and this sensation makes part of the abstract, or rather
indefinite conception.

In fact, all which is not actually present to the mind--and the present
is an infinitesimal fraction of knowledge--is reproduced by the memory,
and this is effected by the molecular movements of the human brain, and
by what may be called the ethereal modifications which took place when
the sensations, perceptions, and acts first occurred. If the cells
vibrate, and the organs of the brain are affected by the recollection of
past ideas and acts, just as when they actually occurred (and this
appears from Schiff's experiences as to the increase of the brain in
heat and volume during dreams), this vibration will be still more marked
when any quality which affects our senses is reproduced in the mind.

The particular _form_ of the quality as it appears in a definite object
is certainly wanting in the abstract conception; it remains in the first