Pop Purim Quiz
Why do we fast today?
1 - To commerate Esther's fast on the 13th of Adar.
2 - To drive home the point that salvation only follows repentance.
3 - Because the Sages say so.
1 - Wrong. Esther fasted for three days in Nissan, not Adar. Though some think we're commerating her three-day fast with our fast today, this is not clear: The Even HaYarchi, for example, believes that all the Jews of Persia fasted on the 13th day of Adar to prepare themselves for the battle which took place the next day. The Even Hayarchi, who did not posess a time machine, bases his belief on Esther 9:19: "And the Jews... congregated on the thirteenth..."Why did they congragte? For fasting, he says.
2 - Wrong. Though this is, perhaps, a good lesson to draw from today's observance, it is very unlikely the Sages sat around the wisdom table plotting out rituals as if they were executives planning a new corporate intiative. It's infinitly more likely that the fast arose, in the same way that costumes and noisemaking arose, with the reasons asigned after the fact.
3 - Correct. We fast today only because the Sages of the Second Temple period ordained it. Though it's fun to work out reasons, we have no way of knowing if any of those reasons were on the minds of the Jews who first fasted, or on the minds of the Sages who ratified the custom after it had become known. I fast because I accept the authority of Chazal in these matters; and if you are fasting today, ultimately, so do you.