The ruler ought also to understand how commonly vices pass themselves off as virtues. For often niggardliness excuses itself under the name of frugality, and on the other hand extravagance conceals itself under the name of liberality. Often inordinate carelessness is believed to be loving-kindness, and unbridled wrath is accounted the virtue of spiritual zeal. Often hasty action is taken for promptness, and tardiness for the deliberation of seriousness. Whence it is necessary for the ruler of souls to distinguish with vigilant care between virtues and vices, lest stinginess get possession of his heart while he exults in seeming frugality in expenditure; or, while anything is recklessly wasted, he glory in being, as it were, compassionately liberal; or, in overlooking what he ought to have smitten, he draw on those that are under him to eternal punishment; or, in mercilessly smiting an offense, he himself offend more grievously; or, by rashly anticipating, mar what might have been done properly and gravely; or, by putting off the merit of a good action, change it to something worse. [Sidenote: No one kind of teaching adapted to all men] Since, then, we have shown what manner of man the pastor ought to be, let us now set forth after what manner he should teach. For, as long before us Gregory Nazianzen,[99] of reverend memory, has taught, one and the same exhortation does not suit all, inasmuch as all are not bound together by similarity of character. For the things that profit some often hurt others; seeing that also, for the most part, herbs which nourish some animals are fatal to others; and the gentle hissing that quiets horses incites whelps; and the medicine which abates one disease aggravates another; and the food which invigorates the life of the strong kills little children. Therefore, according to the quality of the hearers ought the discourse of teachers to be fashioned, so as to suit all and each for their several needs, and yet never deviate from the art of common edification. For what are the intent minds of hearers but, so to speak, a kind of harp, which the skilful player, in order to produce a tune possessing harmony, strikes in various ways? And for this reason the strings render back a melodious sound, because they are struck indeed with one quill, but not with one kind of stroke. Whence every teacher also, that he may edify all in the one virtue of charity, ought to touch the hearts of his hearers out of one doctrine, but not with one and the same exhortation. [Sidenote: Various classes of hearers to be distinguished] Differently to be admonished are these that follow: Men and women. The poor and the rich. The joyful and the sad. Prelates and subordinates. Servants and masters. The wise of this world and the dull. The impudent and the bashful.