nowledge extends indefinitely beyond the range of the pupil's
acquaintance. It involves principles which are beyond the immature
pupil's understanding and interest. In and of itself, it may no
more represent the living world of the pupil's experience than the
astronomer's knowledge of Mars represents a baby's acquaintance with the
room in which he stays. In the second place, the method of organization
of the material of achieved scholarship differs from that of
the beginner. It is not true that the experience of the young is
unorganized--that it consists of isolated scraps. But it is organized in
connection with direct practical centers of interest. The child's home
is, for example, the organizing center of his geographical knowledge.
His own movements about the locality, his journeys abroad, the tales of
his friends, give the ties which hold his items of information together.
But the geography of the geographer, of the one who has already
developed the implications of these smaller experiences, is organized
on the basis of the relationship which the various facts bear to
one another--not the relations which they bear to his house, bodily
movements, and friends. To the one who is learned, subject matter is
extensive, accurately defined, and logically interrelated. To the
one who is learning, it is fluid, partial, and connected through
his personal occupations. 1 The problem of teaching is to keep the
experience of the student moving in the direction of what the expert
already knows. Hence the need that the teacher know both subject matter
and the characteristic needs and capacities of the student.

2. The Development of Subject Matter in the Learner. It is possible,
without doing violence to the facts, to mark off three fairly typical
stages in the growth of subject matter in the experience of the learner.
In its first estate, knowledge exists as the content of intelligent
ability--power to do. This kind of subject matter, or known material, is
expressed in familiarity or acquaintance with things. Then this material
gradually is surcharged and deepened through communicated knowledge or
information. Finally, it is enlarged and worked over into rationally or
logically organized material--that of the one who, relatively speaking,
is expert in the subject.

I. The knowledge which comes first to persons, and that remains most
deeply ingrained, is knowledge of how to do; how to walk, talk, read,
write, skate, ride a bicycl