Aristotle had a bit to say on the subject of poets and historians in his work, The Poetics. An interesting translation of that can be found at http://www.gutenberg.org/ebooks/1974
When Aristotle is describing poets, he is referring to authors of epics eg Homer, which in our contemporary terms we can consider applying to a novelist.
For Aristotle, the historian is one who tells what happened, whereas the poet is one who tells the sort of thing that can happen. A further look into this reveals Aristotle seeing the poet telling the things that according to likelihood or necessity can happen. Another translation of the relevant phrase in Chapter 8, describes this as telling what is possible according to the law of probability or necessity.
A key difference between Aristotle's poets and historians is that of Universals and particulars. The Universals are things that a certain kind of person tends (or would) say or do, according to likelihood or necessity. Thus the poet is telling of Universals. This could be seen as a universal law or rule applying to all. By way of analogy, we have all burned ourselves at some point in our life and learned something from it - burning hurts. Consequently it is highly likely or probable that everyone would seek to avoid being burned again in order to avoid the associated pain.
Aristotle better defines the particulars in Chapter 23 and these present not a single action expected of all but the things occurring in a single period to one person of to many events but with little connection. And that is how Aristotle sees the historian's role, in recording the specifics of an event or single person's adventures, or alternatively the compilation of events without necessary connection.
So what have I learned? That Aristotle, considered in many respects the father of fiction with his rules for writing epics and tragedies, draws a very clear distinction between historians and what we would call novelists. These views can be seen echoed in current debates and arguments about what is history, what is fiction and what, if any, relationship is there between them.