ntact 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
margin. Thus we see that it is a tendency of the mind to be forever
changing. If left to itself, it would be in ceaseless fluctuation, the
whim of every passing fancy. This tendency to fluctuate comes with more
or less regularity, some psychologists say every second or two. True,
we do not always yield to the fluctuating tendency, nevertheless we are
recurrently tempted, and we must exercise continuous effort to keep a
particular object at the focus. The power to exert effort and to
regulate the arrangement of our states of mind is the peculiar gift of
man, and is a prime function of education. Viewed in this light, then,
we see that the voluntary focusing of our attention consists in the
selecting of certain objects to be attended to, and the ignoring of
other objects which act as distractions. We may conveniently classify
the latter as external sensations, bodily sensations and irrelevant
ideas.

Let us take an actual situation that may arise in study and see how
this applies. Suppose you are in your room studying about Charlemagne,
a page of your history text occupying the centre of your attention. The
marginal distractions in such a case would consist, first, in external
sensations, such as the glare from your study-lamp, the hissing of the
radiator, the practising of a neighboring vocalist, the rattle of
passing street-cars. The bodily distractions might consist of
sensations of weariness referred to the back, the arms and the eyes,
and fainter sensations from the digestive organs, heart and lungs. The
irrelevant ideas might consist of thoughts about a German lesson which
you are going to study, visions of a face, or thoughts about some
social engagement. These marginal objects are in the mind even when you
conscientiously focus your mind upon the history lesson, and, t