e equal to zero, but in
one case the zero expresses the fact that there is nothing, in the other
that we have two equal quantities of opposite sign which compensate and
neutralize each other. The unconsciousness of a falling stone is of the
former kind: the stone has no feeling of its fall. Is it the same with
the unconsciousness of instinct, in the extreme cases in which instinct
is unconscious? When we mechanically perform an habitual action, when
the somnambulist automatically acts his dream, unconsciousness may be
absolute; but this is merely due to the fact that the representation of
the act is held in check by the performance of the act itself, which
resembles the idea so perfectly, and fits it so exactly, that
consciousness is unable to find room between them. _Representation is
stopped up by action._ The proof of this is, that if the accomplishment
of the act is arrested or thwarted by an obstacle, consciousness may
reappear. It was there, but neutralized by the action which fulfilled
and thereby filled the representation. The obstacle creates nothing
positive; it simply makes a void, removes a stopper. This inadequacy of
act to representation is precisely what we here call consciousness.

If we examine this point more closely, we shall find that consciousness
is the light that plays around the zone of possible actions or potential
activity which surrounds the action really performed by the living
being. It signifies hesitation or choice. Where many equally possible
actions are indicated without there being any real action (as in a
deliberation that has not come to an end), consciousness is intense.
Where the action performed is the only action possible (as in activity
of the somnambulistic or more generally automatic kind), consciousness
is reduced to nothing. Representation and knowledge exist none the less
in the case if we find a whole series of systematized movements the last
of which is already pre-figured in the first, and if, besides,
consciousness can flash out of them at the shock of an obstacle. From
this point of view, _the consciousness of a living being may be defined
as an arithmetical difference between potential and real activity_. _It
measures the interval between representation and action._

It may be inferred from this that intelligence is likely to point
towards consciousness, and instinct towards unconsciousness. For, where
the implement to be used is organized by nature, the material furni