In prop theory, only certain imaginary games are authorized for any given prop. But for specific props the authorized games do not just specify what is fiction (i.e. true in the fictional world of the game) but assert a claim to fact. For instance, if we watch a news report, the film we watch is a prop just as much as any artwork, and has its own imaginary game, fictional world and so forth. The only difference between this and a fictional story is that the fictional world of the new report is also authorized as fact.
We can easily confirm this: we could watch an identical report as part of a movie and it would be fiction, so the prop itself (the report) does not distinguish between fact and fiction. Everything we imagine is the same in both cases. But the news report, by virtue of being presented as news, gains the authority to be believed as well as imagined. Walton says “what is true is to be believed, what is fictional is to be imagined” but I would say “whether it is fact or fiction, it is to be imagined; if it is authorised as fact, it is also to be believed true”.
What I find fascinating about a news programme as a prop is just what is authorised as fact: there is “news” i.e. stories about death, injury, violence, disaster, crime, war, crowds, anger, money, power, technology and knowledge, but also “sport” and “weather”. We do not think twice about this, yet sport is reporting the events of imaginary games (i.e. sporting matches) as factual, that is, lending authority to what would otherwise be ‘just a game’. Similarly, the weather forecast is authorised as fact, even though it is obviously far closer to fiction (as anyone who has tried to rely upon the Met office for an accurate prediction of the British weather will attest!).
Thus the only distinction between fact and fiction is that what is fact is authorised to be believed as true, as well as being fictional. Rather than fact and fiction being polar opposites, fact is simply a different kind of imaginary game, that which has the authority to make a claim to truth. Fact is not the opposite of fiction, but a different kind of fiction.