should discover not alone whether the facts learned have entered the
memory, but whether they have sunk down into the understanding, so
that they can be used in the acquisition of further education.

_c. The pupil's points of failure and the cause thereof._--Every
teacher has been surprised many times to discover weak places in the
pupil's work when everything had seemingly been thoroughly learned.
With the best teaching these weak places will occasionally occur. It
is not less essential to know these points of failure than to know the
foundations of knowledge which the pupil has already mastered. For
these weak spots must be remedied as we go along if the later work is
to be successful. Very frequently classes are unable to proceed
satisfactorily because of lack of thoroughness in the foundation work
which precedes. To know where a pupil is failing is the first
requisite if we are to help him remedy his weakness.

But not only must the teacher know where the pupil is failing, but
also the cause of his failure. Only when we know this can we
intelligently apply the remedy for the failure. A physician friend of
mine tells me that almost any quack can prescribe successfully for
sickness if he has an expert at hand to diagnose the case and tell him
what is the matter. This is the hardest part of a physician's work and
requires the most skill. So it is with the teacher's work as well. If
we are sure that a certain boy is failing in his recitations because
he is lazy, it is not so difficult to devise a remedy to fit the case.
If we know that another is failing because the work is too advanced
for his preparation, we select a different remedy. But in every case
we must first know the cause of failure if we hope to prescribe a
remedy certain to produce a cure.