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.
For this reason poetry is something more scientific and serious than history, because poetry tends to give general truths while history gives particular facts.
By a "general truth" I mean the sort of thing that a certain type of man will do or say either probably or necessarily. That is what poetry aims at in giving names to the characters. [Note] A "particular fact" is what Alcibiades did or what was done to him.
In the case of comedy this has now become obvious, for comedians construct their plots out of probable incidents and then put in any names that occur to them. They do not, like the iambic satirists, write about individuals. [Note]
In tragedy, on the other hand, they keep to real names. The reason is that what is possible carries conviction. If a thing has not happened, we do not yet believe in its possibility, but what has happened is obviously possible. Had it been impossible, it would not have happened.