[FOM] geometry and non-well-founded sets

Robert Black Mongre at gmx.de
Thu Sep 13 03:35:44 EDT 2007

Someone once said to me (and it sounds true) that using a 
non-well-founded set theory you could so axiomatize projective 
geometry that *both* a line is identified with the set of points 
lying on it *and* a point is identified with the pencil of lines 
passing through it. Can anyone give me a reference for somewhere this 
is actually done?


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