The wall: knowledge

The second wall was harder to see coming.

Language requires the whole world as context. “I saw the man with the telescope.” Which one had the telescope, you or the man? The words alone do not settle it. You need to know what is plausible, what is common, and what the conversation has been about.

That knowledge is ordinary. You use it automatically, without effort or instruction. A computer does not have it unless it is somehow supplied.

And most of it is hard to supply, not just because there is so much of it, but because it does not come neatly packaged as rules. It is built into experience.