法律AI从业者终于有了一个严肃的理论框架来理解RAG的失败原因——不是模型不够大，而是检索架构与法律知识的本质不匹配。做法律科技或合规自动化的团队，建议仔细读读这篇，能帮你避开很多坑。
本文指出，检索增强生成（RAG）在法律AI中的失败并非简单的模型幻觉，而是概率检索与法律知识层次、时间性和制度结构之间的架构不匹配。作者从法律理论出发，提出法律知识具有层次性、动态性和因果可追溯性三个本体论属性，并对应识别出三种检索病理：整体性盲视、历时性盲视和因果不透明性。通过分析现有方法，作者认为它们未能将这些要求视为共同构成性因素，并提出了四个确定性设计方向：本体优先、事件具体化、双时正确性和确定性交互协议。该框架主要关注法律规范适用问题，而非下游任务。
Beyond Probabilistic Similarity: Structural, Temporal, and Causal Limitations of Retrieval-Augmented Generation in the Legal Domain
Retrieval-Augmented Generation (RAG) has become a standard architectural response to unreliability in legal AI, yet high-profile failures, including fabricated citations submitted to courts and anachronistic legal content presented as current, continue to appear across jurisdictions. We argue that these failures are not residual confabulations to be eliminated by scaling language models, but symptoms of an architectural mismatch between probabilistic retrieval and the hierarchical, temporal, and institutional structure of legal knowledge. We develop the argument in three moves. First, we articulate the ontological commitment of legal knowledge as a triad of properties derivable from classical legal theory: hierarchical and mereological structure, diachronic dynamism under operational closure, and causal traceability of institutional provenance grounded in the duty of justification. Second, we identify three corresponding pathologies of retrieval (mereological blindness, diachronic blindness, and causal opacity), each developed with an operational definition, a failure mechanism, a canonical example, and detection criteria for diagnostic use. Third, we review the state of the art through this lens, showing that existing approaches address these requirements unevenly and do not yet compose into a paradigm that treats them as co-constitutive. From this analysis we derive four architectural commitments that characterize the deterministic-by-design direction for legal retrieval: ontological primacy, event reification, bitemporal correctness, and deterministic interaction protocols. The framework concerns quaestio juris (which norms apply and in what state) rather than the downstream tasks that act on identified norms, and addresses legislative and constitutional retrieval primarily, with interpretive time as an explicit extension.