This paper examines the ontological structure underlying Jewish dietary laws (kashruth) and U.S. legal categories, focusing specifically on the ways tacit knowledge has impacted the development and continued use of these organizational systems. In presenting examples of religious legal classifications alongside those formed through secular institutions, I emphasize the academic and professional importance of viewing them as interdependent phenomena. Although religious/secular divisions are frequently introduced in a well-intended attempt to preserve the autonomy of one or both, I argue that such a framing obscures how tacitly acquired social values, preferences, and beliefs operate in disregard of this artificial separation. Building from canonical scholarship on heuristic reasoning (Kahneman and Tversky 1979) and perceptual categories (Rosch 1975), this paper uses an extensive kashruth case study to propose a scaffolded qualitative methodology for identifying the presence of tacit knowledge within KO systems and analyzing its influence on category structure.