The original version encompassed the preceding year, "from the last Day of Atonement until this one." Then, in the 12th century, Meir ben Samuel, the son-in-law of the revered French rabbi Rashi, altered the wording to reflect the year to come, arguing that pre-emptive annulment was more in keeping with the letter and spirit of the Nedarim, the Talmudic treatise on vows. Ben Samuel also added to the prayer the phrase "we do repent [of them all]," which aligned it more closely with purpose of atonement. His version has been taken up by the bulk of the Ashkenazim, while the Sephardim continue to prefer the older, retroactive one.
From its inception, Kol Nidre never attained universal sanction or appeal. Five of the heads of the Babylonian rabbinical academies rejected it outright, claiming that it undermined both the sanctity of personal vows as well as the necessary custom for canceling them. Nevertheless, the prayer gained traction in the other lands of the diaspora. It came in handy on the Iberian Peninsula during the Inquisition when Marranos—Spanish Jews who pretended to convert to Christianity to escape persecution—were forced to make bogus professions of faith in public and needed the winking dispensation of God to do so.
Jewish authorities have often sought to clarify Kol Nidre's intention, while occasionally advocating for its abolition on the grounds that it is theologically worthless. One popular objection to it has been that ignorant Jews would misinterpret the prayer as a license for deceit and treachery—just as anti-Semites have. The prayer was cited as justification for the Oath More Judaico, a humiliating and sadistic legal vow Jews were for centuries forced to swear before testifying in European courts. It wasn't until the middle of the 19th century that most of the Continent began revising or removing it in earnest. (Romania's remained on the books until 1902.) Perhaps in response to this history of vulgar misinterpretation, Jews themselves have had a hard time deciding what to do with the prayer.A rabbinical conference in Brunswick in 1844 ruled unanimously that Kol Nidre was superfluous and should be eliminated from the entire religious tradition. This decision led numerous congregations in Western Europe and many more Reform congregations in the United States to do just that, or to replace the words of the prayer with a Hebrew psalm while retaining its elegiac melody. Orthodox and Conservative congregations still recite the words.
Whichever way one sides in this antique dispute, it's obvious that the line separating conviction and rhetoric in human discourse has always been blurry. "Lord, if you let the harvest come, I'll marry my neighbor's lazy-eyed daughter" was no more feasible or enforceable in the Dark Ages than "If Bush wins, I'm moving to Canada" was in 2000. Modern parlance has a host of throat-clearing clauses to cancel whatever sentiment follows, often in the same sentence, from "Don't hold me to this" to "Dude, I'm not saying, I'm just saying." And it's hard to imagine how the long, proud history of recreational Yiddish cursing would have progressed had Judaism not afforded this wiggle room with respect to anathemas ("May all the teeth fall out of your head except one, and may that one turn brown and rot.")
There's even an esoteric or Straussian reading of Kol Nidre. According to the Kabbalah, the prayer is actually intended as a two-way pact with the Almighty, absolving him of any vows he might make in the coming year that could affect his mortal creation. A man-made allowance for God to rescind promises of plague, pestilence, and Jobian misery suggests not just wishful thinking but a lack of trust in the wisdom and surety of his judgments. Heresy and agnosticism run not far behind. I'm not saying, I'm just saying.