The Undefined Criterion: A Critical Examination of "Novelty" in Scientific Peer Review

"Lack of novelty" is among the most common reasons for manuscript rejection in scientific peer review. Yet a systematic examination reveals that "novelty" lacks a rigorous definition in the philosophy of science. Neither Popper's falsificationism nor Kuhn's paradigm theory explicitly values novelty for its own sake. This paper argues that the absence of a clear definition enables arbitrary gatekeeping, particularly against interdisciplinary research that synthesizes existing knowledge rather than generating new data. Through a case study of a rejected physics manuscript, I demonstrate how undefined novelty criteria create a logical trap: work that connects established frameworks across domains is dismissed as "speculative" despite extensive empirical validation in practice. I propose that scientific evaluation should replace the undefined criterion of "novelty" with assessable criteria such as predictive power, explanatory unification, or practical validation. The paper concludes that the current emphasis on undefined novelty constitutes a structural barrier to scientific progress, particularly for synthetic and interdisciplinary contributions.