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"That is a tree" is a true statement if, and only if, that is a tree.
Which part of that is meta-language, and what makes it so? — creativesoul

I'm not seeing a need for a meta-language; but the repetition of an identical perspective is somewhat less than revealing.

"That is a tree" is a true statement if the subject "that" matches the definition of "tree."

If she receives no treats, her belief is false. Her expectation did not correspond with fact. — creativesoul

And the result of an intelligent system is feedback; her memory is updated to include that outcome. So her confidence in that outcome has gone down a bit, and the next time she hears rustling plastic in won't be as convincing to her that treats will ensue.

And the result of an intelligent system is feedback; her memory is updated to include that outcome. So her confidence in that outcome has gone down a bit, and the next time she hears rustling plastic in won't be as convincing to her that treats will ensue. — AngleWyrm

Indeed. That is precisely how it works.

"That is a tree" is a true statement if, and only if, that is a tree.
Which part of that is meta-language, and what makes it so?
— creativesoul
I'm not seeing a need for a meta-language; but the repetition of an identical perspective is somewhat less than revealing.

"That is a tree" is a true statement if the subject "that" matches the definition of "tree." — AngleWyrm

Yes. That example could be rendered as such. It could also be an example of naming, for the first time, I mean. If it was a first time naming, the original coining, the definition would be in the process of being established, so the matching wouldn't have what it takes yet. A difference between truth and meaning.

The typical example uses cats and mats, which doesn't quite allow the same rendering.

I do not subscribe to meta-language. On my view, it all about meta-cognition. There is no assumption of an infinite tower of meta-cognitions. We think about thought and belief, and it doesn't require another language. We can take proper account of the role that truth has in all thought, belief, and statements thereof with one language(albeit adding complexity). It requires getting thought and belief right. Those things exist prior to language. So, language is already doing the job that meta-language is found incapable of.

To be clear...

I'm not claiming that all thought and belief is prior to language. Some clearly cannot be. Others clearly are. I've yet to read a proper account of this. Conventionally speaking...

If the content of thought and belief is propositional and propositions require language, then so too does thought and belief.

Of course that premiss is dead wrong. The content of all thought and belief is not propositional, it's correlation(s). All propositions consist of correlation(s). All is proposition is correlation. Not all correlation is proposition. Being propositional requires prior meaning. All meaning consists of correlation(s). So...