arious upper harmonics of it which differ from one instrument
to another. They are not separately heard by the ear; they blend with
the fundamental note and suffuse it, and alter it."[41] Let the
attention be directed to these overtones, however, and they at once
detach themselves from their surroundings and step forth into the light
of day. Even so the ticking of the clock may pass unnoticed in the sense
that it is an undiscriminated element in the background of our
consciousness; but if the ticking comes to a sudden stop, the feeling of
a void in our consciousness proclaims the fact that something has gone
out from it.

The observation and description of the facts of consciousness, then, is
based directly on the fact that experience, as the psychologist deals
with it, possesses a focus and margin. Nature as conceived by the
physical sciences presents no such distinction. The facts are what they
are, and their character as focal or marginal, as clear or obscure,
depends altogether upon their relation to an intelligence. Or we may say
that if the facts of experience were always focal and never marginal, it
would never occur to us to speak of consciousness as we do at present.
As long as we confine ourselves to a given color, shape or temperature,
as experienced focally, we are not dealing with consciousness, but with
objects. An analysis of such facts that does not bring in the marginal
is not an analysis of consciousness, but an analysis of physical
reality. Even if we consider non-physical objects, such as mathematical
or economic concepts, we find that our analysis is not psychological
as long as the marginal is left out. The consideration of the margin,
however, brings us into the presence of facts which are of a distinctive
kind and which warrant a new science. Let the margin be eliminated and
psychology disappears at the same time.

The psychological doctrine of focus and margin, then, is a matter of
fundamental importance. On the interpretation of this doctrine depend
our systems of psychology and of philosophy. What, then, is meant by
focus and margin? If we turn to our psychologies, we seem to be
confronted once more with something that everybody knows and nobody can
define. But since we have to do with a distinction, the obligation to
differentiate cannot be wholly ignored. Consciousness is sometimes
likened to a visual field and sometimes to the waves of the sea. Like
the visual field it has a foreground and