Unity and simplicity are salient features of poetry as in painting. Especially dramatic poetry requires wise choice of subject and good diction as to the character building, representations, length of play, number of actors etc. A writer must be cautious in his choice of language. He should prefer subject within his power to properly follow a correct order which will enable him to say right thing at the right moment, so that by means of skillful combination he give a fresh tone to familiar terms and may even coin words in moderation as old poets used to do. In order to get hold of hearer's soul, poetry should be as such befitting different age groups of audience. Therefore a writer must take a subject equal to his strength. This will help him to express his feelings most happily as well as make audience listen that they are able to bear.
Let us take an example of a drama, where the tragic and the comic are distinct though occasionally they overlap. To fulfill all the above mentioned things, a poetry must appeal to the feelings of an audience and the language must be adapted to the characters impersonated. If there will be lack of such agreement everybody will either laugh or fall asleep. It will be better to follow a tradition or invent a continuous story. Achilles, Medea, Orestes etc must be portrayed as they are known to us in Greek literature. Whilenew characters must be handled with consistentencyof their own. It will be quite right to dramatize some Homeric themes, where the characters introduced have well known traits rather than attempt something distinctly original. Make a simple beginning like that of the Odyssey, where the sequel becomes clearer and increases in brilliancy. Homer indulges in no lengthy introduction, but hurries on with his narrative, omits what he cannot adorn and never loses the central theme of his story. Study of the 'strange eventful history' of human life and noting the characteristics of several ages of man is pivotal for a successful play so that the different periods may not be confused. The beauty of of poem is not enough. It must possess charm that leads to hearer's soul where they will. As man's faces smile on those who smile, so they respond to those who weep. If one wants to make one weep, then that person must feel the grief himself first. Sad tones befits the faces of sorrow, blustering accents that of anger, jests become merry and solemn words the grave.
Eventually it will be apt to say that it is impossible to understand the importance of Horace's Ars Poetica for the subsequent history of literature. Since its composition,it has exerted a perpetual influence over poets and literary critics. Horace's injunction that the decorum in choosing words suitable to age, sex,occupation and deposition of characters should be strictly followed. It happens frequently that advancing years bring blessings with them while on the other hand, take away few of them as they retire. So a youth is assigned the part of his age or a boy that of manhood, to come up with complementary acts fitted to their age. In this way, relationship between this exercise to the stage tradition which is extended back through Plautus to New comedy is carried forward. A writer should observe the characteristics of each age of man to prevent audience from laughing or falling asleep and instigate them to assimilate most out of their work.