[Avodah] Yom Kippur x 2

[Zev Sero]

Jonathan Dickson wrote:
 
> My question is, why is there no second day Yom Kippur? The usual answer 
> to this is because people can't fast two days, but if that's the case, 
> why not at least have an issur melacha on 11th Tishri? Or perhaps allow 
> people to eat after nightfall on the 11th, because of pikuach nefesh, 
> and then (having removed the risk) require them to fast for the rest of 
> the 11th?

We only keep yom tov sheni because the same Sanhedrin that established
the fixed calendar ordered us to continue the custom of our ancestors.
Our ancestors in Bavel didn't keep two days of Yom Kippur because of
the sakana in fasting for two days, so we have no reason to do so either.
Nevertheless, the Maharil (quoted by the Ramo) seems to suggest that
there were substantial numbers of people who did fast the second day,
enough that it's worth discussing what they should do if there's a
minyan of them!

-- 
Zev Sero                      The trouble with socialism is that you
zev at sero.name                 eventually run out of other people’s money
                                                     - Margaret Thatcher