This paper delves into the complexities and theoretical underpinnings of knowledge organization systems (KOS), focusing on domain analysis and facet analysis as methodologies, such as improving the Library of Congress Subject Headings (LCSH). The study repeats a former critique of the LCSH and argues for the incorporation of facet and domain analysis to enhance its utility and academic rigor. Facet analysis, although well-established, is critiqued for its rationalist philosophy and lack of empirical grounding. Domain analysis is presented as a complementary approach that addresses these gaps by considering empirical, historical, philosophical, and pragmatic issues. To any given system, the paper emphasizes that KO systems are not neutral; they reflect underlying theoretical paradigms that must be understood for effective classification. The study concludes by advocating for interdisciplinary research and broader cooperation among knowledge organization professionals, philosophers, and subject specialists to develop more robust and academically rigorous KOS.