Why language models hallucinate

I like that OpenAI is drawing a clear line on what “hallucination” means, giving examples, and showing practical steps for addressing them. The post isn’t groundbreaking, but it helps set the tone for how we talk about hallucinations.

What bothers me about the hot takes is the claim that “all models do is hallucinate.” That collapses the distinction entirely. Yes, models are just predicting the next token—but that doesn’t mean all outputs are hallucinations. If that were true, it’d be pointless to even have the term, and it would ignore the fact that some models hallucinate much less than others because of scale, training, and fine-tuning.

That’s why a careful definition matters: not every generation is a hallucination, and having good definitions let us talk about the real differences.

if you insist that they are different, then please find one logical, non-subjective, way to distinguish between a hallucination and not-a-hallucination. Looking at the output and deciding "this is clearly wrong" does not count. No vibes.

> Looking at the output and deciding "this is clearly wrong" does not count.

You need the ground truth to be able to make that determination, so using your knowledge does count. If you press the model to answer even when it does not know, you get confabulation. What today's models lack is the ability to measure their confidence, so they know when to abstain.