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Timeline for To be is to be an element?

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Aug 31, 2021 at 0:38 comment added Frode Alfson Bjørdal @PeterLeFanuLumsdaine It indeed has such a provenance. The terminology I opted for has bearings upon how we think about some important problems. Yes, there are many free logics, with non-denoting terms. The approach I suggest has advantages, it seems. To wit: (1) The mere subsistence, and thus also non-existence, of proper classes, combines well with the idea that classes merely abbreviate formulas. (2) It provides a nice semantics for fictional characters, by including them in the domain of discourse, while making statements as SH is F and SH is not-F false (if we have choice-negation).
Aug 30, 2021 at 18:46 comment added Peter LeFanu Lumsdaine What you describe sounds formally just like a two-sorted set/class theory (e.g. Gödel–Bernays and similar) but with different terminology, saying “$a$ exists” for what would conventionally be read as “$a$ is a set”. Is this what you have in mind, or if not, what difference besides terminological are you thinking of? Systems with terms denoting not-necessarily-existing things have certainly been defined (e.g. Fourman/Scott’s partial logic), but in all such systems I know, “$a$ exists” is equivalent to “$\exists x\ (x=a)$”, i.e. what you’re calling “$x$ subsists”.
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Sep 7, 2021 at 3:07
Aug 30, 2021 at 17:04 history edited Frode Alfson Bjørdal CC BY-SA 4.0
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Aug 30, 2021 at 16:46 history asked Frode Alfson Bjørdal CC BY-SA 4.0