References to public interest are abundant in legal scholarship, jurisprudence, and legislation. However, the meaning of interest still remains rather a common sense idea without legible standards or criteria. The article offers to conceptualize it in a broader socio-historical context, as this concept cannot be treated in isolation from the evolution of the Western scientific paradigm that aspires to rationalize the world, to rationally explain and construct a cognitive map of both social and natural environments. To explore the history of “interest” in law means to grasp and reconstruct the phases of the fundamental revolution that legal thought has undergone since the mid-XVIII century. The article offers a bird-eye view of how the concept of interest gained currency and infiltrated law. This evolutionary perspective could explain certain coherence and similarity of various meanings proposed for the concept of interest in case law and scholarship. The article argues that interest becomes socially recognizable and viable when it is perceived and interpreted as such. It acquires validity in legal argumentation if it fits into the cultural schemata of legal framing. The article purports to deconstruct interest as a category. It argues that three key assumptions underpin the concept: (1) interests are social constructs; (2) interests are generated by argumentation (to qualify as interest an existing or perceived good, purpose, motive, aspiration, or claim requires argumentation that triggers “frames of interest” - cognitive representations and constructs); (3) interests are vehicles whereby normative ideas of justice, society, and the world, generated and validated by other normative orders, are adapted, legitimized and incorporated into law. The article discusses the practical implications of these assumptions. In a judicial proceeding, public interest analysis should explore the central organizing idea of a public interest argumentation against three analytical components: (1) substantive (refers to the interest analysis); (2) quantitative (refers to the “society”/ “public” analysis); and (3) qualitative (refers to analysis focusing on whether the argumentation triggers cognitive representations and constructs that reference moral principles). Finally, the reconceptualization of interest as a social construct can shed new light on legal argumentation and the so-called “five I-s of legal reasoning”: intuitiveness, incidentality, indeterminacy, ideology, and irrationality. Though indeed often intuition-driven, interest as a social construct that fits into legal framing is not incidental, indeterminate, or irrational. Incrementing and unfolding via interaction and competition with discourses and legal frames, interests bring in certainty, predictability, and determinacy to open-ended concepts of law.