<![CDATA[Background: Epistemic reasoning constitutes a fundamental component of scientific literacy because it reflects how students construct, evaluate, and justify scientific knowledge through discourse. Objective: This study aims to map the profile of students' epistemic reasoning through the convergence of the Nature of Scientific Knowledge (NOSK) and Higher Order Thinking Skills (HOTS) manifested in argumentative discourse. Methods: The study employed a descriptive qualitative design involving 16 first-year students in the Biology Education Study Program at the University of Lampung. Data were collected through Focus Group Discussions (FGDs) and analyzed using discourse-based deductive coding across discourse segments. Results: The findings revealed the dominance of the empirical dimension (24.36%) and HOTS analysis (23.08%), whereas the sociocultural dimension (3.85%), creativity (6.41%), HOTS evaluation (8.97%), and HOTS creation (5.13%) remained relatively low, indicating a tendency toward verification-oriented reasoning. Conclusion: Based on the convergence of these empirical findings, this study proposes the Discourse-Based Epistemic Reasoning Theory (DERT) as a middle-range theory explaining that the quality of epistemic reasoning emerges from the interaction between epistemic structures (NOSK) and higher-order cognitive operations (HOTS) manifested through argumentative discourse, with implications for the quality of scientific literacy. This study contributes empirically, methodologically, and conceptually to the advancement of biology education.]]>
