SOLID: Infusing Symbolic Logic into LLMs via Dual-Verified Backward Reasoning

Weijie Yu, Yuhang Dong, Feifei Ma


Abstract
Large Language Models (LLMs) often struggle with rigorous logical reasoning, suffering from hallucinations and inconsistent deduction. Chain-of-Thought (CoT) prompting relies heavily on the frozen model’s inherent capabilities, while neuro-symbolic approaches face a "translation reliability" bottleneck in which semantic parsing errors mislead external solvers. Recent work attempts to infuse symbolic capabilities via fine-tuning, but typically mimics forward reasoning, suffering from search-space explosion and irrelevant intermediate facts that dilute attention. We propose SOLID (Symbolic Oriented Logic Infusion via Dual-verification), a framework that synthesizes high-quality supervision through a Dual-Verification Mechanism: bidirectional consistency checks filter out hallucinated translations. Crucially, instead of forward chaining, we execute validated translations to generate backward reasoning traces—verifying necessary premises from the goal. By fine-tuning on these focused, goal-oriented paths, SOLID infuses the model with the efficient deduction process of a symbolic engine. Experiments on ProntoQA, LogicNLI, and ProofWriter demonstrate state-of-the-art accuracy, significantly outperforming CoT baselines, solver-based methods, and forward-chaining variants. Code and data are available at: https://github.com/ejie22/SOLID.
Anthology ID:
2026.emnlp-main.1528
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
34852–34869
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1528/
DOI:
Bibkey:
Cite (ACL):
Weijie Yu, Yuhang Dong, and Feifei Ma. 2026. SOLID: Infusing Symbolic Logic into LLMs via Dual-Verified Backward Reasoning. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 34852–34869, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
SOLID: Infusing Symbolic Logic into LLMs via Dual-Verified Backward Reasoning (Yu et al., EMNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.emnlp-main.1528.pdf