in the shape of the mind of their opponent.  The mind of your own enemy, the pupil, is working away from you as keenly and eagerly as is the mind of the commander on the other side from the scientific general.  Just what the respective enemies want and think, and what they know and do not know, are as hard things for the teacher as for the general to find out.  Divination and perception, not psychological pedagogics or theoretic strategy, are the only helpers here.

But, if the use of psychological principles thus be negative rather than positive, it does not follow that it may not be a great use, all the same.  It certainly narrows the path for experiments and trials.  We know in advance, if we are psychologists, that certain methods will be wrong, so our psychology saves us from mistakes.  It makes us, moreover, more clear as to what we are about.  We gain confidence in respect to any method which we are using as soon as we believe that it has theory as well as practice at its back.  Most of all, it fructifies our independence, and it reanimates our interest, to see our subject at two different angles,—­to get a stereoscopic view, so to speak, of the youthful organism who is our enemy, and, while handling him with all our concrete tact and divination, to be able, at the same time, to represent to ourselves the curious inner elements of his mental machine.  Such a complete knowledge as this of the pupil, at once intuitive and analytic, is surely the knowledge at which every teacher ought to aim.

Fortunately for you teachers, the elements of the mental machine can be clearly apprehended, and their workings easily grasped.  And, as the most general elements and workings are just those parts of psychology which the teacher finds most directly useful, it follows that the amount of this science which is necessary to all teachers need not be very great.  Those who find themselves loving the subject may go as far as they please, and become possibly none the worse teachers for the fact, even though in some of them one might apprehend a little loss of balance from the tendency observable in all of us to overemphasize certain special parts of a subject when we are studying it intensely and abstractly.  But for the great majority of you a general view is enough, provided it be a true one; and such a general view, one may say, might almost be written on the palm of one’s hand.

Least of all need you, merely as teachers, deem it part of your duty to become contributors to psychological science or to make psychological observations in a methodical or responsible manner.  I fear that some of the enthusiasts for child-study have thrown a certain burden on you in this way.  By all means let child-study go on,—­it is refreshing all our sense of the child’s life.  There are teachers who take a spontaneous delight in filling syllabuses, inscribing observations, compiling statistics, and computing the per cent.  Child-study will certainly