PurposeThis study introduces Simone Weil's impersonal justice concept and its relevance to libraries' identity and role in societies. The article presents the constituents of impersonal justice and a theoretical justification for the coexistence of neutrality with libraries' commitment to social causes.Design/methodology/approachConceptual analysis of 3 Weil's works, 13 scientific articles and 12 libraries' official documents was applied, looking at relevant concepts and findings, contexts of use, arguments and types of authority.FindingsFive constituents of impersonal justice were found: universality, concreteness, unicity, inviolability and inappropriability. Impersonal justice, based on the inviolable value of each individual and the universal expectation of good, allows for a more accurate definition of social justice. Besides, it justifies libraries' commitment to climate change, migrants and Black lives matter, among other causes.Originality/valueIn contrast to previous works, this paper focuses on clarifying concepts by applying conceptual analysis to Weil's works, Library and Information Science (LIS) sources in scientific and normative contexts. Additionally, the analysis of arguments and types of authority for justifying claims pro and against neutrality allows the reconstruction of the argumentative discourse beyond the examined sources.