Meaning is what lasts.
Everything we keep — code, records, recordings, contracts — keeps the steps and loses what they were for.
This is about keeping the meaning instead: what that would take, and how far it might reach, from software to the animals to the sky.
A substrate is the layer underneath that everything else is built on, and that none of it owns. A meaning substrate is one that holds what something means, written once, so that many different things can each work from the same source.
Take a piece of music. The composer writes it down once, as a score. The score is not the sound, and it is not any one instrument. It is what every instrument is working from. Each player is handed a part copied from it, the violin its line and the drums theirs, and because every part comes from the same score, an orchestra of different instruments plays the same piece, together.
Nothing like that exists yet for what something means. Everything we build keeps the steps — the code, the procedure, the recipe — and what they were for stays in someone's head, or in a note nobody updated. When that person leaves, it is gone.
A meaning substrate is the missing one: a way of writing down what a thing is for that no single language or tool owns, in a form a computer can read and check, instead of a form only a human can guess at.
Once the meaning is written down, it becomes the thing you keep, and the steps become something a computer can work out from it — the way a map works out a route from an address, and quietly finds another one when a road closes. Over and over, differently each time if it needs to. A different machine, a faster way of doing it, a change in the world underneath: same meaning, new steps, and you didn't have to rewrite anything.
It also lets you ask questions nobody can really answer today. What is this thing for? Does it still do what we said it would? Did that change alter what it means, or just how it was worded? Right now every one of those questions is answered by a person reading through the steps and guessing.
Nothing about this is really about writing software. Anything that carries meaning has the same problem: we keep the thing itself, and lose what it was for.
Each of those fields has spent years building its own way of working out meaning, and none of them can talk to any of the others. Whether one store could hold all of it is an open question — nobody has done it, and it might not be possible. That is the half worth arguing about, and it is worth reading not because it is right, but because it might be.