and of sensations from your bodily organs, such as the heart and lungs.
In addition to these sensations, you will find, if you introspect
carefully enough, that your mind also contains a number of ideas and
imaginings; thoughts about the paragraph you just read or about one of
your lessons. Thus we see that at a time when we apparently focus our
attention upon but one thing, we really have a large number of things
in our mind, and they are of a great variety. The mental field might be
represented by a circle, at the centre of which is the object of
attention. It may be an object in the external world perceived through
one of the senses, or it may be an idea we are thinking about, such,
for example, as the idea of infinity. But whether the thing attended to
is a perception or an idea, we may properly speak of it as the object
of attention or the "focal" object. In addition to this, we must
recognize the presence of a large number of other objects, both sensory
and ideational. These are nearer the margin of the mental field, so we
call them "marginal."

The distinctive thing about a state of mind such as that just described
is that the focal object is much clearer than the marginal objects. For
example, when you fixated the letter O, it was only in the vaguest sort
of fashion that you were aware of the contact of your clothing or the
lurking ideas of other lessons. As we examine these marginal objects
further, we find that they are continually seeking to crowd into the
centre of attention and to become clear. You may be helped in forming a
vivid picture of conditions if you think of the mind as a stream ever
in motion, and as it flows on, the objects in it continually shift
their positions. A cross-section of the stream at any moment may show
the contents of the mind arranged in a particular pattern, but at the
very next moment they may be arranged in a different pattern, another
object occupying the focus, while the previous tenant is pushed to the