Luther’s Catholic opponents were not the first to offer such warnings. Medieval rabbis had long before concluded that sincerity, inspiration and zeal were no guarantors of right guidance. Explaining the grave error of the Karaite Jews, a Babylonian sect who had called for the rejection of the Oral Torah tradition by which rabbis explained the written books of Moses, the Andalusian rabbi Judah HaLevi noted that sincerity of intention is useless. ‘For that which appears plain in the Torah is yet obscure, and much more so are the obscure passages.’
