The inner and more intimate agreement of words and nature.
If one wishes to look deeply into the nature of the human mind and to search out its inner sources of delight, he will find there something of strength conjoined with something of weakness, and out of this circumstance arises variety and irregularity. The mind's vexation with a continual relaxation derives from its strength, while from its weakness stems the fact that it cannot bear a continual straining. Hence it is that nothing pleases the human mind very long, nothing that is all of one piece. So in music it rejects a wholly perfect harmony, and for this reason musicians deliberately intercalate discordant sounds—what are technically called dissonances. So, finally, it happens that physical exercise, even if it was at first undertaken for pleasure, becomes a torture when continued without interruption.
This point has its pertinence to literature, the more so since in that field nature reveals the greatest delicacy and cannot long endure what is lofty and excited. Yet on the other hand, whatever creeps close to earth and never lifts its head is, if it be prolonged, wearisome. To stand, to rest, to rise up, to be thrown down, this is what every reader or listener desires, and from this derives the driving necessity for variety, for the mingling of the majestic and slight, excited and calm, high and low. But it may seem that this consideration has little pertinence to the epigram, which is brief and so in less need of variety. However, I need not apologize for introducing these more general considerations since others of more immediate pertinence to the course of our discussion are derived from them, and particularly the question of the discriminate use of metaphors, which are of considerable effect in adorning or vitiating poetry.
For if we consider attentively why men are pleased with metaphors we will find no other reason than that already stated: the weakness of nature which is wearied by the inflexibility of truth and plain statement and must be refreshed by an admixture of metaphors which depart somewhat from the truth. This gives the clue to the proper and legitimate use of metaphors; they are to be employed specifically, as musicians employ discordant sounds, to relieve the distaste of perfect harmony. But how frequently and at what point they should be introduced is a matter of considerable caution and skill. One warning will suffice for the present: that metaphors, hyperboles, and whatever varies from the plain and natural way of saying something should not be sought for their own sakes but as a kind of relief for nauseated nature. They are to be accepted on grounds of necessity, and consequently a good deal of moderation must be observed in their use. Thus Quintilian rightly says, "A sparing and opportune use of these figures gives lustre to speech; frequent use obscures and fills with disgust."[6] You will discover this fault often in many epigrams, especially in those of contemporary writers as I shall show by several examples later on. However, lest this doctrine should issue in too strict an austerity of diction, it should be noted that only those expressions are to be taken as metaphors that are remote from ordinary usage and offer the mind a double idea. Hence if a metaphor is so commonplace that it no longer has a figurative connotation and suggests nothing other than the notion itself for which it is used, then it should be numbered among proper rather than metaphorical expressions and does not fall in that class of tropes whose too frequent use is here censured.