Aristotle goes so far as to say that probability, not actuality, controls
the structure of a narrative or dramatic plot in that, "what follows
should be the necessary or probable result of the preceding action,"[23]
even to the extent that the poet should prefer probable impossibilities to
improbable possibilities, for by a logical fallacy even an irrational
premise in an action may seem probable provided that the conclusion is
logical and made to seem real.[24] For instance, the irrational elements
in the Odyssey "are presented to the imagination with such vividness and
coherence that the impossible becomes plausible; the fiction looks like
truth."[25] Such a result occurs only when the characters and action are
made real. We believe that which we see, even though we know in our hearts
that it is not so.

How important Aristotle feels it to be that the spectator or reader should
see before him the characters and situations of an epic or drama is
evinced by his suggestion to the poet on the process of composing. The
author, he says, should visualize the situations he is presenting, working
out the appropriate gestures, for he who feels emotion is best at
transmitting it to an audience.[26] It is only when the poet thus
completely realizes his characters and situations that the audience can be
induced to feel sympathetically the pity and fear which produces the
_katharsis_, so important a result of successful tragedy. If human beings
did not possess that tendency to feel within themselves the emotions of
the people on the stage, they would be unable to experience vicariously
the fear animating the tragic hero. Thus tragedy, which is the type of all
poetic, depends vitally, according to Aristotle, on imaginative
realization.