It seems therefore that all those poets are wrong who have written a or or other such poems.Aristotle condemns them all, assuming—or perhaps assured by experience—that their sole claim to unity lay in the fact that all the stories in the poem had a common hero. They think that because Heracles was a single individual the plot must for that reason have unity.

But Homer, supreme also in all other respects, was apparently well aware of this truth either by instinct or from knowledge of his art. For in writing an he did not put in all that ever happened to Odysseus, his being wounded on Parnassus, for instance, or his feigned madness when the host was gathered(these being events neither of which necessarily or probably led to the other), but he constructed his round a single action in our sense of the phrase. And the the same.

As then in the other arts of representation a single representation means a representation of a single object, so too the plot being a representation of a piece of action must represent a single piece of action and the whole of it; and the component incidents must be so arranged that if one of them be transposed or removed, the unity of the whole is dislocated and destroyed. For if the presence or absence of a thing makes no visible difference, then it is not an integral part of the whole.

What we have said already makes it further clear that a poet’s object is not to tell what actually happened but what could and would happen either probably or inevitably.

The difference between a historian and a poet is not that one writes in prose and the other in verse— indeed the writings of Herodotus could be put into verse and yet would still be a kind of history, whether written in metre or not. The real difference is this, that one tells what happened and the other what might happen.