ABED: Assumption-Based Bidirectional Entailment Diagnosis for Open-World Logical Reasoning

Seyeon Jeong, Sojeong Park, Beakcheol Jang


Abstract
Open-world logical entailment requires deciding whether a set of premises entails a conclusion, entails its negation, or leaves it undecided. Many existing methods are deductive in spirit, searching for a proof and reading the label from whether that proof succeeds. When implemented through LLM-based proof search, this makes the prediction depend on a single unstable trajectory, and a failed or partial search is easily mismapped to the wrong label. We propose ABED (Assumption-Based Bidirectional Entailment Diagnosis), a training-free inference-time framework that reframes entailment classification as missing assumption diagnosis. Instead of asking only whether a conclusion can be proved, ABED asks what assumption is missing for it to hold, and classifies that gap as already closed by the premises (Null), contradicted by them (Contra), or left open (Admissible). It applies this diagnosis to both a conclusion and its negation, and determines the label from the resulting dual gap pair. Across FOLIO, ProofWriter, ProntoQA, and LogicNLI, ABED consistently outperforms prompting-based, symbolic, solver-based, and deductive baselines, improving over the strongest baseline on each dataset by 3.4, 5.3, 0.8, and 4.4 points with GPT-4.1.
Anthology ID:
2026.emnlp-main.2193
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:
49852–49876
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2193/
DOI:
Bibkey:
Cite (ACL):
Seyeon Jeong, Sojeong Park, and Beakcheol Jang. 2026. ABED: Assumption-Based Bidirectional Entailment Diagnosis for Open-World Logical Reasoning. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 49852–49876, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
ABED: Assumption-Based Bidirectional Entailment Diagnosis for Open-World Logical Reasoning (Jeong et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2193.pdf