Tanas objects: “Not sure I understand what existential conservativism would amount to. Wouldn't you agree that there is a detective in A.C.Doyle' stories?”. Agreed. A classic problem for theories of fiction, particularly ‘existentially conservative’ ones, is to explain how there can be true statements such as ‘Sherlock Holmes was a detective’.
But I should clarify what I mean by ‘existential conservatism’. Suppose someone says ‘Louis XIV had an adviser called D’Artagnan’. Without qualification, that is false. As far as we know, that French King had no such advisor. It is true that, in his "Muskeeters" stories, the novelist Dumas says the French King had such an adviser. And we say that ‘In the stories, Louis had an adviser called D’Artagnan’, or ‘According to Dumas &c’. I'm sure everyone agrees that the fictional statement is not true in an unqualified sense, and requires some qualifying statement such as ‘according to …’ or ‘in the story …’
So we agree up to this point. We disagree, I imagine, on the explanation of these qualifying statements. According to the conservative, the logical form of ‘According to S, p’ is ‘S says that p’. This can be true, even though p is false, for we are truly reporting that someone (or some story says) that p, not reporting that p itself. Thus ‘Sherlock Holmes is a detective’ is false without qualification. In a qualified sense, i.e. as meaning ‘According to the Holmes stories, Holmes is a detective’ it is true. Similarly ‘There are such things as hobbits’ is false, without further qualification. Taken as meaning ‘In Tolkien’s world’, or ‘According to Tolkien’ it is true.
According to existential liberals, on the other hand, the qualifying phrase directs us to a story-world or fictional universe, which really exists, in some sense, and which the story is truly about. Thus ‘there are hobbits in Tolkien’s world’ says of a really existing, but parallel fictional world described by Tolkien, a race of creatures called hobbits exist.
Who is right? According to the conservative, there is no argument evidence or evidence to support the existence of fictional worlds or fictional creatures or people, beyond the need of explaining the truth of statements like ‘Hobbits have furry feet’ or ‘Holmes was a detective’. But given we can explain the truth of such statements in terms of ‘S says that p’, which does not require the positing of an extra universe of things, we should prefer the more conservative explanation, which does not multiply things according to the multiplicity of terms. Or so the original Ockham would have argued.
 By extraordinary coincidence, if it is that, Peter Smith is dealing with a very similar issue here.