30.  As then the same medicine and the same food are not in every case administered to men’s bodies, but a difference is made according to their degree of health or infirmity; so also are souls treated with varying instruction and guidance.  To this treatment witness is borne by those who have had experience of it.  Some are led by doctrine, others trained by example; some need the spur, others the curb; some are sluggish and hard to rouse to the good, and must be stirred up by being smitten with the word; others are immoderately fervent in spirit, with impulses difficult to restrain, like thoroughbred colts, who run wide of the turning post, and to improve them the word must have a restraining and checking influence.