that if one knows a certain field of subject-matter, he will
surely be able to teach it to others. But nothing could be further from
the truth than such an assumption. Indeed, it is proverbial that the
great specialists are the most wretched teachers of their subjects. The
nature of the child's mental powers, the order of their unfoldment, the
evolution of his interests, the incentives that appeal to him, the
danger points in both his intellectual and his moral development,--these
and many other things about child nature the intelligent teacher must
clearly understand.

And the teacher of the younger children needs this knowledge even more
than the teacher of older ones. For the earlier years of the child's
schooling are the most important years. It is at this time that he lays
the foundation for all later learning, that he forms his habits of study
and his attitude toward education, and that his life is given the bent
for all its later development. Nothing can be more irrational,
therefore, than to put the most untrained and inexperienced teachers in
charge of the younger children. The fallacious notion that "anyone can
teach little children" has borne tragic fruit in the stagnation and
mediocrity of many lives whose powers were capable of great
achievements.

_The teacher must know the subject-matter._ The blind cannot
successfully lead the blind. One whose grasp of a subject extends only
to the simplest rudiments cannot teach these rudiments. He who has never
himself explored a field can hardly guide others through that field; at
least, progress through the field will be at the cost of great waste of
time and failure to grasp the significance or beauty of what the field
contains.

Expressed more concretely, it is impossible to transplant arithmetic, or
geography, or history, or anything else that one would teach,
immediately from the textbook into the mind of the child. The subject
must first come to be very fully and completely a true possession of the
teacher. The successful teacher must also know vastly more of a subject
than he is required to teach. For only then has he freedom; only then
has he outlook and perspective; only then can he teach the _subject_,
and not some particular textbook; only then can he inspire others to
effort and achievement through his own mastery and interest. Enthusiasm
is _caught_ and not taught.

_The teacher must know the technique of instruction._ For teaching is an
art, based