Toni Lassila a écrit : > On 7 Jul 2006 13:30:05 -0700, "Nathan" <email@example.com> wrote: > >> Mike Deeth wrote: >> >>> It's well-known that a countable union of finite sets is countable. >> Nope! You said you were working in ZF. This requires AC. > > No it doesn't.
Even a countable union of pairs can be uncountable (Cohen). You should check your sources.