Aristotle Rhetoric 3.8

[1] The form of diction should be neither metrical nor without rhythm. If it is metrical, it lacks persuasiveness, for it appears artificial, and at the same time it distracts the hearer's attention, since it sets him on the watch for the recurrence of such and such a cadence; just as, when the public criers ask, Whom does the emancipated ¹ choose for his patron? the children shout Cleon.

[2] If it is without rhythm, it is unlimited, whereas it ought to be limited (but not by meter); for that which is unlimited is unpleasant and unknowable. Now all things are limited by number, and the number belonging to the form of diction is rhythm, of which the meters are divisions. ²

[3] Wherefore prose must be rhythmical, but not metrical, otherwise it will be a poem. Nor must this rhythm be rigorously carried out, but only up to a certain point.

[4] Of the different rhythms the heroic is dignified, but lacking the harmony of ordinary conversation; the iambic is the language of the many, wherefore of all meters it is most used in common speech; but speech should be dignified and calculated to rouse the hearer. The trochaic is too much like the cordax; this is clear from the tetrameters, 1409a 1 which form a tripping rhythm. There remains the paean, used by rhetoricians from the time of Thrasymachus, although they could not define it.

The paean is a third kind of rhythm closely related to those already mentioned; for its proportion is 3 to 2, that of the others 1 to 1 and 2 to 1, with both of which the paean, whose proportion is 1 1/2 to 1, is connected. ³

[5] All the other meters then are to be disregarded for the reasons stated, and also because they are metrical; but the paean should be retained, because it is the only one of the rhythms mentioned which is not adapted to a metrical system, so that it is most likely to be undetected.

[6] At the present day one kind of paean alone is employed, at the beginning as well as at the end; ⁴ the end, however, ought to differ from the beginning. Now there are two kinds of paeans, opposed to each other. The one is appropriate at the beginning, where in fact it is used. It begins with a long syllable and ends with three short: and The other on the contrary begins with three short syllables and ends with one long one: This is a suitable ending, for the short syllable, being incomplete, mutilates the cadence. But the period should be broken off by a long syllable and 20 the end should be clearly marked, not by the scribe nor by a punctuation mark, ⁶ but by the rhythm itself.

[7] That the style should be rhythmical and not unrhythmical, and what rhythms and what arrangement of them make it of this character, has now been sufficiently shown.