The Complete Aristotle (eng.)

where
something is proved to be or not to be, or a general maxim is
enunciated.
    Fourth among the elements enumerated comes Diction; by which I
mean, as has been already said, the expression of the meaning in
words; and its essence is the same both in verse and prose.
    Of the remaining elements Song holds the chief place among the
embellishments
    The Spectacle has, indeed, an emotional attraction of its own,
but, of all the parts, it is the least artistic, and connected
least with the art of poetry. For the power of Tragedy, we may be
sure, is felt even apart from representation and actors. Besides,
the production of spectacular effects depends more on the art of
the stage machinist than on that of the poet.
VII
    These principles being established, let us now discuss the
proper structure of the Plot, since this is the first and most
important thing in Tragedy.
    Now, according to our definition Tragedy is an imitation of an
action that is complete, and whole, and of a certain magnitude; for
there may be a whole that is wanting in magnitude. A whole is that
which has a beginning, a middle, and an end. A beginning is that
which does not itself follow anything by causal necessity, but
after which something naturally is or comes to be. An end, on the
contrary, is that which itself naturally follows some other thing,
either by necessity, or as a rule, but has nothing following it. A
middle is that which follows something as some other thing follows
it. A well constructed plot, therefore, must neither begin nor end
at haphazard, but conform to these principles.
    Again, a beautiful object, whether it be a living organism or
any whole composed of parts, must not only have an orderly
arrangement of parts, but must also be of a certain magnitude; for
beauty depends on magnitude and order. Hence a very small animal
organism cannot be beautiful; for the view of it is confused, the
object being seen in an almost imperceptible moment of time. Nor,
again, can one of vast size be beautiful; for as the eye cannot
take it all in at once, the unity and sense of the whole is lost
for the spectator; as for instance if there were one a thousand
miles long. As, therefore, in the case of animate bodies and
organisms a certain magnitude is necessary, and a magnitude which
may be easily embraced in one view; so in the plot, a certain
length is necessary, and a length which can be easily embraced by
the memory. The limit of length in relation to dramatic competition
and sensuous presentment is no part of artistic theory. For had it
been the rule for a hundred tragedies to compete together, the
performance would have been regulated by the water-clock—as indeed
we are told was formerly done. But the limit as fixed by the nature
of the drama itself is this: the greater the length, the more
beautiful will the piece be by reason of its size, provided that
the whole be perspicuous. And to define the matter roughly, we may
say that the proper magnitude is comprised within such limits, that
the sequence of events, according to the law of probability or
necessity, will admit of a change from bad fortune to good, or from
good fortune to bad.
VIII
    Unity of plot does not, as some persons think, consist in the
unity of the hero. For infinitely various are the incidents in one
man’s life which cannot be reduced to unity; and so, too, there are
many actions of one man out of which we cannot make one action.
Hence the error, as it appears, of all poets who have composed a
Heracleid, a Theseid, or other poems of the kind. They imagine that
as Heracles was one man, the story of Heracles must also be a
unity. But Homer, as in all else he is of surpassing merit, here
too—whether from art or natural genius—seems to have happily
discerned the truth. In composing the Odyssey he did not include
all the adventures of Odysseus—such as his wound on Parnassus, or
his feigned madness at the mustering of the host—incidents between
which there was no necessary or probable connection: but he made
the Odyssey, and likewise the Iliad, to center round an action that
in our sense of the word is one. As therefore, in the other
imitative arts, the imitation is one when the object imitated is
one, so the plot, being an imitation of an action, must imitate one
action and that a whole, the structural union of the parts being
such that, if any one of them is displaced or removed, the whole
will be disjointed and disturbed. For a thing whose presence or
absence makes no