Whilst looking for a message in the ont-forum archives I just
happened to notice that I asserted The False in a recent post; I wrote: (01)
> John S. wrote:
>> The critical distinction between set theory and mereology
>> is that the axioms of set theory generate something new:
>>
>> For any x, the set {x} is distinct from x.
>
> Yes, in well-founded set theories like Zermelo-Fraenkel set theory,
> but singletons are perhaps the wrong thing to focus on to highlight
> the distinction in question, as there are in fact so-called non-well-
> founded set theories in which x = {x}. (02)
That should have read "in which there are sets x such that x = {x}".
That equation obviously does not hold across the board (consider,
e.g., the empty set for a simple counterexample). (03)
Chris Menzel (04)
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