Plato - Image Source: ourcivilisation.com
Plato didn't believe that the concept of mimesis had any place in an ordered society. In his Republic he states, through Socrates, that while he appreciates the art, in his utopia, poets would be honoured but turned from the gates of the cities. (It is interesting to note that his great polemic was mimetic in form, however.)
...and, further, they are harmful to those who hear them. Everyone will be sympathetic with himself when he is bad, persuaded that after all similar things are done and were done even by [gods]… We'll forbid them to say such things.
(PLATO) BLOOM, 1968. P.70
This distrust of poets and performers is one that is echoed, even by poets and performers themselves:
"Our poets keep long nails and untrimmed hair, much in solitude, shunning baths."
However, Aristotle believes that "Imitation is natural to man..." and that we learn first by imitating others. The idea that theatre could be used as an educational tool, that by watching a theatrical performance could be a learning experience, is also shared by Plato, although he takes this to the extreme and believes, therefore, that there should be restrictions placed on what can, or cannot, be presented on stage.
Aristotle - Image Source: britannica.com
During Aristotle's time, theatre became concerned with spectacle and scenic effects, removing theatre further from its origins in storytelling or religion. Neither Aristotle, nor Horace, appreciated the spectacle, both arguing that the best poets (playwrights) ought not to rely on scenic effects, rather on the strength of the plot. Both philosophers believe that tragic actions should not happen on stage, but ought to be described after the event. Horace admits that "A thing when heard, remember, strikes less keen on the spectator's mind than when 'tis seen." but that this would generate disgust rather than empathy, and empathy, and therefore catharsis, is perceived as being one of the main aims of the theatrical experience.
Aristotle strongly believed in the cathartic power of theatre, and considered the arts without reference to social, moral or religious purposes. He states that "incidents arousing pity and fear" in a performance can accomplish a "catharsis of such emotions" in the watching audience. This is something that is still considered to be the 'point' of theatre; watching a character experience a challenging situation, or strong emotions, allows us to empathise because we are experiencing the emotions simultaneously with the actor on stage; an experience that other forms of performance (modern film, television, etc) cannot replicate to the same degree.
I disagree in part with Aristotle's theory of the unities of theatre (time, place, action, character etc.) and many modern plays destroy the unities entirely, even down to something as simple as doubling up on the characters or having action take place in two separate places. However it provides a simple, linear layout for a production or plot, which is still useful.
"The youth who runs for prizes wisely trains,
Bears cold and heat, is patient and abstains:
The flute-player at a festival, before
He plays in public, has to learn his lore.
Not so our bardlings: they come bouncing in -
'I'm your true poet: let them laugh that win:
Plague take the last! although I ne'er was taught,
Is that a cause for owning I know naught?' "
I adore this passage from Horace; the idea that even in Ancient times those higher up the professional ladder took umbrage with untrained newcomers. This is a situation that our profession still hasn't overcome! I agree with him on this, although at times his ire seems misdirected and he heaps scorn on everyone involved in the creation of theatre, from the actors and writers to the audience themselves. It makes me wonder whether he actually enjoyed his job!
Horace - Image Source: crystalinks.com
Theatre was considered to be educational and edifying. It was a unifying experience across most social classes and castes, and even the layout of the theatres reflects this; sat in the round, with the speaker in the centre. The ancient philosophers and poets; Aristotle, Horace and Plato, provided the roots of Western Theatre tradition, the effects of which are still apparent in many modern productions.