Chapter XXXVII. Of the exhortation to be applied to one person, who labours under contrary passions. It is indeed a serious labour for the preacher to keep an eye in his public preaching to the hidden affections and motives of individuals, and, after the manner of the palæstra, to turn himself with skill to either side:  yet he is worn with much severer labour, when he is compelled to preach to one person who is subject to contrary vices.  For it is commonly the case that some one is of too joyous a constitution, and yet sadness suddenly arising immoderately depresses him.  The preacher, therefore, must give heed that the temporary sadness be so removed that the constitutional joyousness be not increased; and that the constitutional joyousness be so curbed that the temporary sadness be not aggravated.  This man is burdened by a habit of immoderate precipitancy, and yet sometimes the power of a suddenly-born fear impedes his doing what ought to be done in haste.  That man is burdened by a habit of immoderate fear, and yet sometimes is impelled in what he desires by the rashness of immoderate precipitancy.  In the one, therefore, let the fear that suddenly arises be so repressed that his long-nourished precipitancy do not further grow.  In the other let the precipitancy that suddenly arises be so repressed that yet the fear stamped on him by constitution do not gather strength.  And, indeed, what is there strange in the physicians of souls being on their guard in these things, when those who heal not hearts but bodies govern themselves with so great skill of discernment?  For it is often the case that extreme faintness weighs down a weak body, which faintness ought to be met by strong remedies; but yet the weak body cannot bear a strong remedy.  He, therefore, who treats the case gives heed so to draw off the supervening malady that the pre-existing weakness of the body be in no wise increased, lest perchance the faintness should pass away with the life.  He compounds, then, his remedy with such discernment as at one and the same time to meet both the faintness and the weakness.  If, then, medicine for the body administered without division can be of service in a divided way, why should not medicine for the soul, applied in one and the same preaching, be of power to meet moral diseases in diverse directions:  which medicine is the more subtle in its operation in that invisible things are dealt with?