ResearchResearch paperLarge Language Models · Reasoning & Planning1 source · Oct 18, 2026

When Form Changes but Logic Doesn't: Building Logic-invariant LLMs through Logical Structure

Large language models (LLMs) have achieved strong performance across diverse reasoning tasks, yet it remains unclear whether this performance reflects an understanding of underlying logical structure or a reliance on shallow semantic cues.

Key points

  • A key indicator of such understanding is whether models treat logically equivalent inputs consistently, producing the same predictions despite differences in expression.
  • Through systematic evaluation on curated data, we show that even strong LLMs often fail this test: they do not consistently preserve predictions across logically equivalent inputs and generalize poorly to unseen logical forms.
  • To address this limitation, we propose LoGIcal STructure-guided reasoning (LoGIST), a framework that guides LLM reasoning with explicit logical structure.
  • Across multiple training settings, LoGIST reduces inconsistency under logical equivalence and improves generalization to unseen logical forms, suggesting that logical invariance is a useful target for building more robust and generalizable logical reasoning in LLMs.

Sources (1)

  • [1]When Form Changes but Logic Doesn't: Building Logic-invariant LLMs through Logical Structure
    arXiv (AI, ML, NLP, CV, robotics, multi-agent) · Oct 18, 04:56 PM
    Large language models (LLMs) have achieved strong performance across diverse reasoning tasks, yet it remains unclear whether this performance reflects an understanding of underlying logical structure or a reliance on shallow semantic cues.
    A key indicator of such understanding is whether models treat logically equivalent inputs consistently, producing the same predictions despite differences in expression.

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