Institutio Oratoria

For just as the melody of the voice is most pleasing when accompanied by the lyre, yet if the musician's hand be slow and, unless he first look at the strings and take their measure, hesitate as to which strings match the several notes of the voice, it would be better that he should content himself with the natural music of the voice unaccompanied by any instrument; even so our theory of speaking must be adapted and, like the lyre, attuned to such rules as these.

But it is only by constant practice that we can secure that, just as the hands of the musician, even though his eyes be turned elsewhere, produce bass, treble or intermediate notes by force of habit, so the thought of the orator should suffer no delay owing to the variety and number of possible arguments, but that the latter should present themselves uncalled and, just as letters and syllables require no thought on the part of a writer, so arguments should spontaneously follow the thought of the orator.

The third kind of proof, which is drawn into the service of the case from without, is styled a παράδειγμα by the Greeks, who apply the term to all comparisons of like with like, but more especially to historical parallels. Roman writers have for the most part preferred to give the name of comparison to that which the Greeks style παραβολή, while they translate παράδειγμα by example, although this latter involves comparison, while the former is of