
Re: Matheology S 224
Posted:
Apr 20, 2013 6:47 AM


Alan Smaill wrote: > > Frederick Williams <freddywilliams@btinternet.com> writes: > > > Nam Nguyen wrote: > >> > >> On 19/04/2013 5:55 AM, Frederick Williams wrote: > >> > Nam Nguyen wrote: > >> >> > >> >> On 18/04/2013 7:19 AM, Frederick Williams wrote: > > > >> > >> > > >> >>> Also, as I remarked elsewhere, "x e S' /\ Ay[ y e S' > y e S]" doesn't > >> >>> express "x is in a nonempty subset of S". > >> >> > >> >> Why? > >> > > >> > It says that x is in S' and S' is a subset of S. > >> > >> How does that contradict that it would express "x is in a nonempty > >> subset of S", in this context where we'd borrow the expressibility > >> of L(ZF) as much as we could, as I had alluded before? > > > > You really are plumbing the depths. To express that x is nonempty you > > have to say that something is in x, not that x is in something. > > but the claim was that x *is in* a nonempty set  > in this case S', which is nonempty, since x is an element of S', > and S' is a subset of S.
Oh, I am so sorry, I did not see the "in" in "x is in a nonempty subset of S", and it seems I didn't see it three or four times. My apologies to Nam.
> (Much though it would be good for Nam to realise that > some background set theory axioms would be kind of useful here)
 When a true genius appears in the world, you may know him by this sign, that the dunces are all in confederacy against him. Jonathan Swift: Thoughts on Various Subjects, Moral and Diverting

