When one hears about religious discussions of doubt, one thinks about those who are unsure in their beliefs. But in his book The Birth of Doubt, Moshe Halbertal examines something else entirely: how the rabbis of the 3rd and 4th centuries CE dealt with situations of halakhic uncertainty, such as a piece of meat that might have been purchased from a kosher butcher, but could possibly have originated from a non-kosher one. Zalman Rothschild writes in his review:
Halbertal makes sense of these disparate and seemingly arbitrary standards for determining permissible consumption [in such cases] by drawing attention to the early rabbis’ sensitivity to the chaotic nature of the public marketplace and human frailty. Early rabbinic authorities appreciated that a purchaser of meat in a busy market is more prone to forgetting from whom he made his purchases. The anxiety surrounding doubt as to the source of the meat and a . . . draconian rule requiring one to assume the worst when in doubt would disincentivize merchants from participating in public markets.
The earliest stratum of rabbinic law, with great foresight and sensitivity, established a [set of rules] according to which the Jewish merchant can enter the marketplace armed with confidence that an entire system of laws would be implicated in any situation of legal doubt, and that this system of laws does not stringently require him to discard something he purchased simply because he doesn’t have near-certainty that it is kosher.
The heaps of laws surrounding states of uncertainty—which Halbertal correctly describes as some of the most complex areas of Jewish law—were not designed, by virtue of their sheer volume and complexity, to increase anxiety but to quell it. Early rabbinic engagement with doubt was thus an expression of liberation, not legal bondage. Its intent was not to compound hair-splitting laws on top of likely never-to-be-experienced hypotheticals for the sake of burdening Jews with laws where none previously existed, thereby adding to their already extensive repertoire of rules. Rather, this complex system was intended to free up the Jewish practitioner.