> If you view the world as a collection of facts, describing even mundane things fully requires an immense number of facts...
We already have some answers here: the resources needed by current LLMs sets an upper bound on what is needed to do what they do, and we can also make a reasonable estimate of the resources used by the human brain to do what it does. In the case of LLMs, there is no mystery about how those resources are put to use, as they were designed and implemented by humans (we may be surprised by how much they can do with those resources being used the way they are - well, I certainly was - but that is not the same thing as the way they use them being a mystery, which is essentially where we are with respect to human brains.)
> I could ask the exact same questions about a human's understanding of the real world...
It is already well-established that by the age of two, infants are developing a rudimentary theory of mind - an understanding that other people have minds - and by around four, they begin to grasp that thoughts in the mind may not be true [1]. These abilities seem to require the recognition of an external world as a prerequisite.
Do LLMs give any indication of doing so? I'm not up-to-date on the research, but the last paper I saw on the topic only seemed to demonstrate that they can sometimes produce sentences as if they did - but, given the way their sentences are generated, it is difficult to say that this means anything more than that these sentences are the sort of sentences that a human is likely to say in the same situation.
Update: this point just occurred to me: LLMs receive tokens, not words. Words have real-world semantics, but, in general, tokens do not. To me, this increases my doubt as to whether LLMs could understand that language is about an external world.
[1] https://www.child-encyclopedia.com/social-cognition/accordin...