Understanding Syllogistic Reasoning in LLMs from Formal and Natural Language Perspectives
Aheli Poddar, Saptarshi Sahoo, Sujata Ghosh
2025-12-23
Summary
This research investigates how well large language models (LLMs) can perform syllogistic reasoning, which is a type of logical argument. It looks at this reasoning from both a purely logical standpoint and how well the models understand the reasoning when it's presented in natural language, like a regular sentence.
What's the problem?
The core issue is understanding what LLMs are actually doing when they appear to reason. Are they truly grasping the underlying logic, or are they just recognizing patterns in the data they were trained on? It's unclear if LLMs are developing genuine reasoning skills or simply mimicking human thought processes, and whether this ability is consistent across different models.
What's the solution?
The researchers tested 14 different LLMs using syllogisms – statements where a conclusion is drawn from two premises. They evaluated the models on their ability to make correct logical deductions (symbolic inferences) and to understand the reasoning when the syllogisms were worded in a natural way. They observed that some models performed perfectly on the logical tasks, raising questions about their reasoning process.
Why it matters?
This work is important because it helps us understand the capabilities and limitations of LLMs. If these models are becoming capable of formal reasoning, it could lead to significant advancements in areas like artificial intelligence and problem-solving. However, it also raises questions about whether they are truly understanding the nuances of human reasoning, which is crucial for building AI systems that can interact with us effectively.
Abstract
We study syllogistic reasoning in LLMs from the logical and natural language perspectives. In process, we explore fundamental reasoning capabilities of the LLMs and the direction this research is moving forward. To aid in our studies, we use 14 large language models and investigate their syllogistic reasoning capabilities in terms of symbolic inferences as well as natural language understanding. Even though this reasoning mechanism is not a uniform emergent property across LLMs, the perfect symbolic performances in certain models make us wonder whether LLMs are becoming more and more formal reasoning mechanisms, rather than making explicit the nuances of human reasoning.