The wall confronting large language models

Pepperoni falls off pizza.

Therefore to keep it in place, stick it with glue...

Not stunned by this reductionist take.

We don't understand what LLMs are doing. You can't go from understanding what a transformer is to understanding what an LLM does any more than you can go from understanding what a Neuron is to what a brain does.

The fundamental autoregressive architecture is absolutely capable of backtracking… we generate next token probabilities, select a next token, then calculate probabilities for the token thereafter.

There is absolutely nothing stopping you from “rewinding” to an earlier token, making a different selection and replaying from that point. The basic architecture absolutely supports it.

Why then has nobody implemented it? Maybe, this kind of backtracking isn’t really that useful.

Take a finite tape Turing machine with N states and tape length T and N^T total possible tape states.

Now consider that you have a probability for each state instead of a definite state. The transitions of the Turing machine induce transitions of the probabilities. These transitions define a Markov chain on a N^T dimensional probability space.

Is this useful? Absolutely not. It's just a trivial rewriting. But it shows that high dimensional spaces are extremely powerful. You can trade off sophisticated transition rules for high dimensionality.

You _can_ continue this line of thought though in more productive directions. E.g. what if the input of your machine is genuinely uncertain? What if the transitions are not precise but slightly noisy? You'd expect that the fundamental capabilities of a noisy machine wouldn't be that much worse than those of a noiseless ones (over finite time horizons). What if the machine was built to be noise resistant in some way?

All of this should regularize the Markov chain above. If it's more regular you can start thinking about approximating it using a lower rank transition matrix.

The point of this is not to say that this is really useful. It's to say that there is no reason in my mind to dismiss the purely mathematical rewriting as entirely meaningless in practice.

Of course, in practice you don't actually get arbitrary degree polynomials but some finite degree, so the approximation might still be quite bad or inefficient.

If you limit yourself to Markov chains where the full transition matrix can be stored in a reasonable amount of space (which is the kind of Markov chain that people usually have in mind when they think that Markov chains are very limited), LLMs cannot be represented as such a Markov chain.

If you want to show limitations of LLMs by reducing them to another system of computation, you need to pick one that is more limited than LLMs appear to be, not less.

The whole analogy is just pointless. You might as well call an elephant an Escalade because they weigh the same.

> Any discrete-time computation (including backtracking search) becomes Markov if you define the state as the full machine configuration. Thus “Markov ⇒ no reasoning/backtracking” is a non sequitur. Moreover, LLMs can simulate backtracking in their reasoning chains. -- GPT-5

Since temperature zero makes it deterministic, you only need to test one step for each state and symbol combination.

Are you suggesting you don't believe you can't make a prompt that successfully encodes 6 trivial state transitions?

Either you're being intentionally obtuse, or you don't understand just how simple a minimal Turing machine is.

From Wikipedia:

Suppose that the program simulated in fine detail the action of every neuron in the brain of a Chinese speaker.[83][w] This strengthens the intuition that there would be no significant difference between the operation of the program and the operation of a live human brain. Not a useful definition of thinking if you ask me.

Searle replies that such a simulation does not reproduce the important features of the brain—its causal and intentional states. He is adamant that "human mental phenomena [are] dependent on actual physical–chemical properties of actual human brains."[26]

I definitely imagine that and I'm surprised to hear you don't. To me it seems obvious that this is how humans reason logically. When you're developing a complex argument, don't you write a sloppy first draft then review to check and clean up the logic?

Unless you can show evidence that unlike the LLMs* we can execute more than the Turing computable, the theoretical limits on our reasoning are exactly the same as that of the LLM.

Absent any evidence at all that we can solve anything outside of the Turing computable, or that any computable function exists outside the Turing computable, the burden of proof is firmly in those making such an outrageous assumption to produce at least a single example of such a computation.

This argumebt doesn't mean any given LLM is capable of reasoning at the level of a human on its own any more than it means a given person is able to translate Chinese on its own, but it does mean there's no basis in any evidence for claiming no LLM can be made to reason just like a human any more than there's a basis for claiming no person can learn Chinese.

> When we claim someone reasons logically we usually don't imagine they randomly throw ideas at the wall and then consult outputs to determine if they reasoned logically

This isn't how LLMs work either, so this is entirely irrelevant.

Who said anything about software engineers?

In essence, thinking of the computations performed as if logged on an infinitely long tape.

Now, an immutable tape without overwrites is at best a finite automaton, but giving it the ability to replace tokens — which we have and can do — gives us an interpreted tape that — in a very handwavey manner and if you really squeeze your eyes — resembles a Turing machine.

So backtracking could be simulated by an LLM, no?

Is there any “difference” under these conditions up to what an LLM can approximate?

Applied demon summoning is ruled by empiricism and experimentation. The best summoners in the field are the ones who have a lot of practical experience and a sharp, honed intuition for the bizarre dynamics of the summoning process. And even those very summoners, specialists worth their weight in gold, are slaves to the experiment! Their novel ideas and methods and refinements still fail more often than they succeed!

One of the first lessons you have to learn in the field is that of humility. That your "novel ideas" and "brilliant insights" are neither novel nor brilliant - and the only path to success lies through things small and testable, most of which do not survive the test.

With that, can you trust the demon summoning knowledge of someone who has never drawn a summoning diagram?

1. Sequence Models relying on a markov chain, with and without summarization to extend beyond fixed length horizons. 2. All forms of attention mechanisms/dense layers. 3. A specific Transformer architecture.

That there exists a limit on the representation or prediction powers of the model for tasks of all input/output token lengths or fixed size N input tokens/M output tokens. *Based On* a derived cost growth schedule for model size, data size, compute budgets.

Separately, I would have expected a clear literature review of existing mathematical studies on LLM capabilities and limitations - for which there are *many*. Including studies that purport that Transformers can represent any program of finite pre-determined execution length.

While it's not a requirement to have published in a field before publishing in a field. Having a coauthor who is from the target field or a peer review venue in that field as an entry point certainly raises credibility.

From my limited claim to be in either Machine Learning or Large Language Models the paper does not appear to demonstrate what it claims. The author's language addresses the field of Machine Learning and LLM development as you would a young student - which does not help make their point.

I'm not saying anything about the content, merely making a remark.