Things, facts, and details can have an "objective" / "external" / "real" / "factual" existence if the frame of reference being used for that language is that of the characters within said setting.
In the fiction, there is a difference between waking and dreaming, and hence between reality and imagination.
But that is clearly not what
@Bedrockgames means when he calls a mystery "real" or "objective", as all the RPGs that I and
@hawkeyefan have posted about draw exactly the same distinction in their fiction.
I am drawing a distinction between something that exists objectively in the setting and something that doesn’t. I.e there is a shop called WAN’S MUTTON STEW. It didn’t arise because the players came to town looking for a mutton stew ship. The GM has created it as part of a specific city, located in a specific area of the empire. So it isn’t an objective detail of the setting. I don’t think it is that outrageous of use. But in a mystery whether the players are solving it hinges on that.
I take it that when you say "So it isn't an objective detail", you actually mean "So it is an objective detail".
I do think this is an outrageous use, in that it is a point of needless jargon - you are using "objective" to mean "pre-authored" (ie it is a detail of the setting that has been pre-authored by the GM without having regard to any player action-declarations or salience/priorities that arise during play). Why you refuse to use the term "pre-authored" to describe the process of
authoring stuff prior to play is a mystery to me.
If the DM created it as part of the setting, how is it not an objective part of the setting?
What work is "objective" doing here? None that I can see.
Here are a couple of extracts from the actual play post I've referred to several times in this thread:
I started by asking the player of Appleby what he was doing in London - his answer was that he was there to hand the documents over to the lawyers, given his master the Earl's mysterious absence. This started a plot thread about the need to obtain a power of attorney from the Earl's trustees - missing from the documents handed over - which took the loyal butler to the well-appointed apartments of Willoughby Smythe, who - it turned out through subequent play - was the Earl's principal guardian with the capacity to execute a power in favour of Mr Jerome the Earl's solicitor.
When I asked Randal's player whether he was likely to be having a meeting at a Mechanics Institute or a gentlemen's club he opted for the latter, and so we played through his meeting with Sir Ronald Livingstone (distantly related to the famous Livingstone of Africa), who revealed an interest in using colonial labour and expansion in East Africa while cultivating markets in America as a way to respond to industrial strife in England. Sir Ronald was called away suddenly, but arranged for Randal to call upon him at his apartments later that evening - which he did, but after taking brandy on his own in the drawing room and waiting for much longer than he had anticipated he smelled smoke, and realised the house was on fire. Running out what seemed to be the safest way, he found himself in Livingstone's first-floor study where Sir Ronald was slumped dead at his desk. A quick look at the books and papers revealed some financial information and what seemed to be a detailed hand-drawn topographic map: he took the latter and jumped out the window (breaking his leg in the process, due to a poor roll, and so he was in a plaster cast and dependant on crutches or a wheelchair for the rest of the session).
The mysterious absence of the Earl was authored by Appleby's player, in response to my asking him why Appleby was in London.
My authoring of Sir Ronald Livingstone, his political and economic concerns, his apartments, his drawing room and brandy, his study, and his books and papers, were all done by me in the course of framing a series of scenes for Randal.
Those things are all clearly parts of the setting. Are they "objective"? They certainly weren't
dreams.
This is also why I said to Pemerton that there are is also middle ground and ask for more information on his examples, because even in these other approaches things can become objective after they are introduced in play
I have posted plenty of information, to little avail.