Great quote from Augustine on variation in style in preaching

51. But we are not to suppose that it is against rule to mingle these various styles: on the contrary, every variety of style should be introduced so far as is consistent with good taste. For when we keep monotonously to one style, we fail to retain the hearer's attention; but when we pass from one style to another, the discourse goes off more gracefully, even though it extend to greater length. Each separate style, again, has varieties of its own which prevent the hearer's attention from cooling or becoming languid. We can bear the subdued style, however, longer without variety than the majestic style. For the mental emotion which it is necessary to stir up in order to carry the hearer's feelings with us, when once it has been sufficiently excited, the higher the pitch to which it is raised, can be maintained the shorter time. And therefore we must be on our guard, lest, in striving to carry to a higher point the emotion we have excited, we rather lose what we have already gained. But after the interposition of matter that we have to treat in a quieter style, we can return with good effect to that which must be treated forcibly, thus making the tide of eloquence to ebb and flow like the sea. It follows from this, that the majestic style, if it is to be long continued, ought not to be unvaried, but should alternate at intervals with the other styles; the speech or writing as a whole, however, being referred to that style which is the prevailing one.


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