To throw light, also, upon things, similes have been invented, some of which by way of proof are inserted among arguments, and others are calculated for expressing the images of things, the point we are here explaining.

                   ...  Thence like wolves

Prowling in gloomy shade, which hunger blind
Urges along, while their forsaken whelps
Expect them with dry jaws. 

          
                                                                    Trapp.

   ...  Thence with all his body’s force

Flings himself headlong from the steepy height
Down to the ocean:  like the bird that flies
Low, skimming o’er the surface, near the sea,
Around the shores, around the fishy rocks. 

          
                                                                      Trapp.

HOW TO EMPLOY SIMILES AND METAPHORS

We must be exceedingly cautious in regard to similitudes, that we do not use such as are either obscure or unknown.  For that which is assumed for the sake of illustrating another thing, ought indeed to be clearer than that which it so illustrates.

In speaking of arguments I mentioned a kind of similitude which, as an ornament to a discourse, contributes to make it sublime, florid, pleasing, and admirable.  For the more far-fetched a similitude is, the more new and unexpected it will appear.  Some may be thought commonplace, yet will avail much for enforcing belief; as, “As a piece of ground becomes better and more fertile by cultivation, so does the mind by good institutions.”  “As physicians prescribe the amputation of a limb that manifestly tends to mortification, so would it be necessary to cut off all bad citizens, tho even allied to us in blood.”  Here is something more sublime:  “Rocks and solitudes echo back the melody, and the fiercest beasts are often made more gentle, being astonished by the harmony of music.”  But this kind of similitude is often abused by the too great liberties our declaimers give themselves; for they use such as are false, and they do not make a just application of them to the subjects to which they would compare them.

In every comparison the similitude either goes before, and the thing follows; or the thing goes before, and the similitude follows.  But the similitude sometimes is free and separate:  sometimes, which is best, it is connected with the thing of which it is the image, this connection being made to aid and correspond mutually on both sides.  Cicero says in his oration for Murena:  “They who have not a genius for playing on the lyre, may become expert at playing on the flute (a proverbial saying among the Greeks to specify the man who can not make himself master of the superior sciences):  so among us they who can not become orators, turn to the study of the law.”  In another passage of the same oration, the connected