I'm no great fan of "true stories," too many of which, disappointingly, aren't true. But I am deeply partial to good made-up stories, like - a favorite - the one about the shtetl showdown between the Jew and the priest. As the tale goes, the governor of a 19th-century Polish village is prevailed upon by a learned non-Jewish cleric to humiliate the town's Jewish populace by issuing it a challenge: "Have your greatest scholar meet me on the bridge over the raging river tomorrow at noon. Each of us will have a heavy weight tied to his foot, and the first one stumped by a question about the Torah, Talmud or commentaries will be cast by the other into the waters." The members of the Jewish community, in no position to refuse the ultimatum, anxiously huddle. "Whom can we send?" they ask. "Who can be assured of being able to answer any question the priest may pose?" "Who could possibly stump the non-Jew?" None of those present offers their services. Until, that is, Shmiel the shneider (tailor) confidently steps forward to volunteer. Known as a decidedly unscholarly fellow, he would not have been anyone's first, or 81st, choice. But he insists he can better the challenger and, well, he's the only candidate. And so, at the appointed time, Shmiel and his opponent take their positions on the bridge, ball and chain attached to each man's foot, a crowd of supporters on each of the river's banks. Surveying the tailor, the non-Jew smiles benevolently and offers Shmiel the first shot. The Jew does not hesitate. "What does eini yode'a mean?" he asks loudly. The cleric, not even pausing to think, shouts out his entirely accurate answer: "I do not know!" The crowd gasps at the response and Shmiel, beaming triumphantly toward the townsfolk, unceremoniously pushes his momentarily confused opponent off the bridge, into the raging waters. The crowds disperse, one jubilant, the other perplexed. Back at the shtetl town hall, Shmiel is roundly congratulated for his ploy. "How did you come up with so brilliant an idea?" they ask. Radiating modesty, Shmiel responds that it wasn't hard at all. "I was reading the teitch (the popular Yiddish translation of the great scholar Rashi's commentary on the Torah)," he explains, "and I saw the words eini yode'a in Rashi's commentary. I didn't know what the phrase meant, and so I looked at the teitch and saw, in Yiddish, the words 'I don't know'. So I figured," Shmiel said, his face aglow with wisdom, "if the holy teitch didn't know what the words meant, there was no way on earth some priest would!" THE STORY is good for more than a laugh, though. Because it raises the interesting and significant fact that Rashi - the "father of all commentaries" who wrote perfectly succinct yet brilliant glosses to not only the Five Books of Moses and Prophets and Writings but to the entire Babylonian Talmud - indeed informs the reader in several places that he "doesn't know" the reason for one or another thing. "I don't know" is a phrase as deserved as it is rare these days, when self-assuredness seems all too often to stand in for self-respect, when opinions are routinely proffered as unassailable fact, when people are permitted - even expected - to state without doubt what they cannot possibly know to be true. Whether in the political, scientific or social realms, opinions regularly take on the aura of convictions. There is, of course, nothing wrong with opinions (for some of us, our stock in trade), but Rashi's modest example is one we would be wise to more often emulate. As the Talmud puts it: "Teach your tongue to say 'I do not know'" (Berachot, 4a). Some of us "know" that the Iraq war was a mistake. Others, that it was precisely the right decision. Some "know" that species evolved from other species. Others, that they didn't. Some "know" that educational vouchers will be terrible for public schools. Others, that they would be wonderful. We think a lot of things, but know a good many less. To be sure, there are verities. That we humans possess a spark of the Divinity that created us, for instance. That we have free will. That life is precious. That our actions have consequences. For Jews, there are - or should be - other certainties, among them that we have been divinely chosen to set an example for the wider world, that our carefully-preserved history includes at its apogee God's bequeathal of His Torah to us, that our mission and our peoplehood are sacred. But there are many smaller things, no end of them, that we do not know, at least not with the certainty of those essential convictions. And so, as we consider wars and theories and causes, even if we think we have a pretty good idea of just what's what, it's always a good idea to stop and remember what Shmiel thought he knew - and what Rashi knew he didn't. Rabbi Avi Shafran is director of public affairs for Agudath Israel of America.