[FOM] counted sets

joeshipman@aol.com joeshipman at aol.com
Thu Aug 20 21:48:48 EDT 2009

I saw Conway yesterday and he confirmed that he remembered inventing 
the term "counted set" but had no reason to believe it had not been 
independently invented by someone else earlier or later. 
In general Chow is correct about getting rid of gadgetry in 
mathematical concepts; but neither Conway nor I could think of an easy 
example of a set which was countable but which had no obvious way of 
counting it. I suppose if there were a set of real numbers which was 
not obviously countable from its definition, but for which there was a 
nontrivial proof that its points were all isolated, one would have a 
countable set that was not "counted". 
-- JS 
-----Original Message----- 
From: Thomas Forster <T.Forster at dpmms.cam.ac.uk> 
> That's a good question. I learnt the terminology from Conway in 
>Cambridge when i was a Ph.D. student there in a previous millenium 
>(I've always assumed the expression is his: Conway does have this 
>*wonderful* gift for snappy names). As to where the nomenclature 
>first appears in print, God knows. It's certainly in my u/g text 
>*Logic, Induction and Sets*, but that surely cannot be its first 
>appearance. There must surely be *somebody* on this list who is 
>based in Princeton and could ask him over coffee one morning? 

More information about the FOM mailing list