[FOM] A confession

T.Forster at dpmms.cam.ac.uk T.Forster at dpmms.cam.ac.uk
Tue Sep 3 17:41:01 EDT 2013


    You have presumably received from me an email about the possibility of 
finding a different way to turn the world of sets into a category. Various 
kind people have pointed out that your proof that the world of NF sets is 
not cartesian-closed puts severe difficulties in the path of any such 
project. It seems that all you need is that NF has a universal set.

**Does this mean that the same result holds for positive set theory?**

And an apology.  Having established by my own methods that the sets of NF 
were not cartesian closed i never troubled to work through your proof.  
That's the trouble with thinking you know everything!  I think my proof 
is useful all the same, since it works for KF as well (indeed for any set 
theory in which the singleton function is not reliably a set, locally) 

Elaine Landry has kindly supplied me with a pdf of your paper (tho' i now 
realise i had a copy on my laptop all the time!!!) So i can get stuck in.

   I would glad to hear any thoughts you have on this matter..

       v best wishes


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