To elaborate on another comment: Jewish law is seldom concerned with absolute certainty; it much more often is a question of degrees of doubt. In many cases two disjoint causes for reasonable doubt about facts that would impact the whether a certain action is forbidden are sufficient to render it permitted. When coming from a mindset of mathematical/logical proof, it can seem like "fuzzy logic" or, as you said, innumerate, but in actuality it's typically more like a hypothesis and the body of evidence that supports it (and depending on the specific hypothesis, a higher or lower degree of certainty may be considered sufficient).