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LLMs Will Always Hallucinate, and We Need to Live With This
arxiv.orgAs Large Language Models become more ubiquitous across domains, it becomes important to examine their inherent limitations critically. This work argues that hallucinations in language models are not just occasional errors but an inevitable feature of these systems. We demonstrate that hallucinations stem from the fundamental mathematical and logical structure of LLMs. It is, therefore, impossible to eliminate them through architectural improvements, dataset enhancements, or fact-checking mechanisms. Our analysis draws on computational theory and Godel's First Incompleteness Theorem, which references the undecidability of problems like the Halting, Emptiness, and Acceptance Problems. We demonstrate that every stage of the LLM process-from training data compilation to fact retrieval, intent classification, and text generation-will have a non-zero probability of producing hallucinations. This work introduces the concept of Structural Hallucination as an intrinsic nature of these systems. By establishing the mathematical certainty of hallucinations, we challenge the prevailing notion that they can be fully mitigated.



They are errors, not hallucinations. Use the right words and then you can talk about the error rate and the acceptable error rate, the same way we do everything else.
An “error” could be like it did a grammar wrong or used the wrong definition when interpreting, or something like an unsanitized input injection. When we’re talking about an LLM trying to convince the user of completely fabricated information, “hallucination” conveys that idea much more precisely, and IMO differentiating the phenomenon from a regular mis-coded software bug is significant.
But calling it an error implies that it can be solved. I’d call it a fundamental design flaw.